US1586232A - Apparatus for drying wood, lumber, and the like - Google Patents

Description

May 25,1926. j 1,586,232

J. B. WELCH APPARATUS FOR DRYING WOOD, LUMBER, AND THE LIKE Filed Sept. 30, 1924 2 Sheets-Sheet l I INVENTOR @WLMLL ATTORNEYS May 25,1926. 1,586,232

J. B. WELC H v APPARATUS FOR DRYING WOOD, LUMBER, AND THE LIKE Filed Sept. 50, 1924 2 Sheets-Sheet 2 |NVE NTOR 301 B. walcj 1' I A 5 ATTORNEYS Patented May 25, 1926,

um-ran STATES 'aoinr nsacnuans wiincn, or new onnmns, LOUISIANA.

PATENT OFFICE.

- arian'rus i on nnYme woon, LUMBER, Am) ran L ma;

1 Application am September so, 1924. Serial No.

I This invention relates to the art of drying materials such as lumber, wood, or the like, 4

f and has for its object theprovisionpf an perature and to provide an apparatus for drying such matethe invention aims drying materials such as lumber or wood, inwhich the temhumidity of the drying medium are automatically cont-rolled in response to changes in a varying characteristic (such improved apparatus for rials. More particularly,

as weight or moisture content) of the material undergoing drying as the drying progresses.

- The. invention relates especially to the dry-' ing of lumber or wood, and will be describedthroughout this specification as applied to that industry. It is to be understood, however, that the principles of the invention are applicable to the drying of other materials where different conditions of temperature and humidity are required in the course of the drying operation.

The controlling factors in the drying of lumber, and of wood generally, are the moisture content of the wood, the thickness of the wood, and the species. Voods which are easily subjectto splitting in drying must be treated at a low temperature and a high humidity. If the wood has a high percentage ofmoisture the starting temperature must be lower and the humidity higher than if the same woodhad been air-dried down to a low moisture content before being put in the drying kiln. In other words, the moisture content of the wood is the controlling factor for any particular thickness and species.

In .the careful drying of wood. the moisture content of the wood is first determined and the appropriate temperature and humidity of the drying medium for that moisture content are thereby established. After the wood has been dried down to a lower moisture content, more severe conditions of temperature and humidit of the drying medium are allowable. eretofore, in the careful drying of wood, it has been necessary for the operator to periodically go into the kiln, take a sample of the wood undergoing drying, and makea moisturedetermination of that sample in order to find out if the moisture content is low enough to permit or warrant a new setting of the conditions of temperature and humidity. In practice,

this necessitates daily weighing of samples from each kiln to determine the appropriate conditions for the dryingoperation. Often,

even in the hands of a skillful operator, the drying roceeds too far before conditions are chang and then again conditions are sometimes. changed before the lumber or wood is dry enough to stand the altered conditions of temperature'and humidity.

The high temperatures and humidity within a lumber drying kiln make the duty of entering the kiln for obtaining samples most arduous, and on this account, the drying is seldom controlled by the moisture content of the wood as it should be, but is more I often based on a time schedule. This schedule is set after the moisture content of the wood is determined and before drying commences. out interruption, goo drying may be accomplished. However, any interruptions in the drying, such as low steam pressure, shutting down of the kilns or boilers for repairs,

changes in weather conditions which affect the temperature within the kiln, and a variety ofother causes, often slow up the actual drying so that the lumber or wood is, not able to stand the increasing temperature and decreasing humidity called for by the drying schedule. As a result, there is often a considerable loss of lumber due to splitting caused by too rapid drying.

. The present invention contemplates an improved apparatus for drying materials,

If everg'thing proceeds with-.

such as wood or lumber, in which the material itself, according to its weight or moisture content, from within the drying kiln, automatically prescribes the appropriate temperature and humidity conditions which are required throughout the entire drying operation. Thus, the invention involves the provision of certain expedients for controlhug and adjusting the conditions of temperature and humidity of the drying medium in responseto the decreasing moisture content of the material undergoing drying. In

controller may be taining the temperature substantially uniform and humidity setting means cooperating with means for maintaining the humidity substantially uniform, of an electromagnet, means for adjusting temperature or humidity, or the temperature and humidity setting means actuated by the electromagnet, means for producing an action indicative of the loss of weight of a re resentativesample of the material being ried as the drying operation progresses, and means'foractuating the electromagnet in response to said v action.

The novel features of the invention-will be more clearly understood from the following description taken in conjunction with the accompanying drawings which diagrammatically illustrate the various features of the invention, in which;

Fig. 1 isa diagrammatic view of a complete setup;'

Fig. 2 is a diagrammatic view of parts of a temperature helical coil (which is similarto the humidity helical coil described below).

respectively, pointer 4 is actuated by a temperature ele- In the drawings I have illustrated temperature and humidity controllers combined in a sm le case and com rising a frame or body 1 aving pivoted tiereon a temperature-setting means or pointer 2 and a humidity-setting means or pointer 3, which are set or adjusted to their appro riate positions ina'manner which will be ereinafter described. -A temperature-indicating pointer 4' and a humidity-indicating pointer 5 are mounted upon the body or frame 1 in operative association with the temperature-setting means 2 and the humidity-setting means 3 The temperature-indicating ment or dry bulb 6. The temperature element or dry bulb 6 is of the usual type,

' containin 'a volatile liquid or gas which,

when sub ected to heat, becomes volatilized and the vapor pressure is transmitted through a flexible tube 7 to a helical coil 8. The movement of the helical coil 8 is transmitted to the temperature-indicating pointer 4 by means of links 9 and 10. The humidityiudicating. pointer 5 is actuated in like manner by the wet bulb 11 through the flexible tube 12, helical coil 13, and links 1 1 and 15.

A duplex valve mechanism 'is mounted upon the body orframe 1 of the-temperature and humidity controllers and comprises .a temperature control valve having a valve chamber 16 which communicates by a passage 17 with a compressed air supply pipe ,18. The valve chamber 16 contains a valve to the atmosphere and simultaneously to 'close or open (respectively) the passage 17.

ing pointer 4 so as to close the air'nozzle 24 as the temperature-indicating pointer moves into apredetermined position with respect 'to the temperature-setting pointer 2.

An air pipe 26 provides communication between the valve chamber 16 and an airoperated steam valve 27 which controls the supply of steam to the kiln. I

The humidity control valve is of similar construction to the temperature control valve and comprises a valve chamber 28 having a passa e 29 connected to the air supply pipe 18. K valve head 30 is adapted to open or close a port 31 to the atmosphere and si-.

multane'ously to close or open (respectively) The valve. head 30' is I the passage 29. mounted on a hollow vah'e stem 32 communicating between the valve chamber 28 and a bellows diaphragm 33. The diaphragni33,-attached to frame 1 in any appropriate manner (not shown), communicates by aflexible tubing 34 with an air nozzle 35 mounted on the humidity-setting pointer 3. A flapper valve 36 is mounted on the humidity-indicating pointer 5 to close the air nozzle 35 as the humidity-indicating pointer 5 approaches Within a predetermined distance of the humidity-setting pointer 3. An air pipe 37 communicates between the valve chamber 28 and an air operated spray valve 38, operating the spray within the kiln.. The air pipe 37 also communicates with a damper valve 39 for opening or closing a damper 40 in the kiln.

v The air lines 18, 26 and 37 are provided withpressure gauges 90 to indicate the air pressure in these lines. 7

As is shown in the drawings, when the valve head 19 closes the ort 20 and opens the passage 17, the'air supp ypipe 18 is in direct communication with the air pipe 26, thereby permitting compressed air to pass into the will remain open. J As the temperature with- -in the kiln rises, the temperature-indicating pointer 4 moves towards the temperature-set ting pointer 2 until the temperature within the kiln reaches the prescribed temperature, whereupon the flapper valve 25 engages and closes the air nozzle 24. This causes. the

air pressure to be thrown back into the bel lows diaphragm 22 which thereupon expands becomes lower, permitting more severe tem- I msaase and moves the valve head 19 to close the passage 17, thereby permitting the compressed air in the pipe 26 and valve 27 to escape to the atmosphere through the: port in the valve chamber'16. The valve 27 thereupon closes and shuts off the steam supply. to the kiln. When the temperature withinthe kiln has again fallen to below the pre-fi scribedtem-perature, the temperature indi-' air nozzle 35 to appropriately operate the i spray valve 38 and the damper valve 39.

As thedrying operation progresses, the moisture content of the material being dried I perature and humidity conditions. It is,

material being driedav =*The control sample 41 is a representative therefore, necessary at various intervals to ad'ust or. move the temperature-setting pointer 2, and the humidity-setting pointer 3 to newpositions, as prescrlbed by the loss in weight or moisture content of the mate-- rial being dried. For this purpose I provide certain novel features for automatically'adjusting the position of the temperature-setting pointer 2- and the humidity setting-- pointer 3 to new positions, as prescribed by the loss "in weight or moisture content of Blythe material beingdried. For this purpose. I provide certain novel features for.auto-- matically adjusting the positions of the temperature-setting pointer 2-and the humidity! setting pointer 3 in response to the loss in r weight of arepresentative sample of the v sample of the wood to bedried and may 1' within the kilnis fairly representative of' the action of that medium throughout the. 'kiln. 1 The sample 41 is carried by a pair of depending gripping 'hooks 142-pivotally mounted near one end of a horiontally posi conveniently be approximately 8 inches wide and 24 inches long. Thissample is plaeed on a special type of scales within the kiln.

- The sample is preferably so ositioned that the action thereon of the rying medium tioned balance arm 43. The' balance arm is operatively-supported a pair of stationmoo.

ary'lmife edges 44 cooperating with notches M ..nar the other end of the arm and by, knife edge support 45 cooperating with knife ed cs 46 above the arm and intermediate its en s but relatively nearer the end cooperating with the knife ed'ges44. Th knife es.

46 are secured to a tube 47. A flexible strap 48is secured at one end to the tube47, which, passing over the top of the tube, is fastened at the other or depending end to the balance arm 43. A depending rod 49 is secured to the tube 47 and carries a counter-balance wei ht 50.

e stationary knife edges 44. and the knife edgesupport 45 may conveniently be mounted on a portable anel 51. This panel may also advantageous y carry the electrical controlling switch or other device of the instrumentallties for transmitting movements of the balance arm 43 to a desired point outside the kiln. The electrical controlling switch comprises a series of contacts 52 electrically connected to one terminal of an electromagnet or relay winding 53, and a second series of contacts 54 electrically connected to one terminal of an electromagnet or relay winding 55. The other terminals of the windings 53 and 55 are electrically connected to' a movable contact 56actuated b the scales arm 43 through .the rod 49 an a connecting member 57 A' battery 58 is in'the common circuit connecings 53 and 55.

An armature piston 59 is operatively arranged to be moved towards the left when the relay winding 53 is energized and towards the right when the relay winding 55 is energized. The piston 59 carries a'pin 60 engaging in a slot in .a rocker cam 61 so that when the winding 53 is energized the cam is turned counter-clockwise, and when the winding 55 is energized the cam is turned clockwise. spring 62 mechanically connects the cam 61 with a movable, switch arm 63 adapted to engage with either of two tion between the contact 56 an'dtthe wind- 4 spring contacts 64 and '65. The camfil is electrically connected to the movable switch arm 63 through the metallic frame. of the instrument or through the. spring 62.;

,- The cam 61-carries two lugs 66 and 67 adapted to engage with and lock the switch contacts 64 and. 65 respectively in such a manner that the piston 59 can move almost its completed-distance towards the winding 53 (or the winding 55) before the spring 62 will act to throw the arm 63 from engagementwith the contact-64 into engage ment-with the contact 65, or vice-versa'.

The piston 59 carries a flexible "contact68 arranged to have a sweeping engagement with-a stationary contact 69 as the piston is moved in response to the energization of first'one and then the other of the windings 53 and 55. The contacts 68 and 69 are included in an electrical circuit with a battery Z0 and an electromagnet .or relay winding QAn armature plunger 72 is operatively mountedflwith respect to the winding 71.

; At its upper or inner end the armature 72 is pivotally connected to a lever arm 73.

which" in turn is pivotally mounted on a shaft or spindle 74. A spring 75 normally holds the lever arm 73 in the position as shown in the drawings. The lever arm 73 carries a spring-pressed pawl 76 cooperating with a ratchet 77 secured to the shaft or spindle 74. Setting screws 78 are provided for determining the movement of the armature 72 each time the winding 71 is energized. Adjustment of the screws 78 permits adjustment of the number of teeth ofthe ratchet 77 moved each time the winding 71 is energized.

The ratchet 77 is always moved in the same direction by the armature 72. A temperature-adjusting-cam 7 9 and a humidityadjusting cam 80 are also secured to the shaft 74:. Movement of the temperature adjusting cam 79 actuates a cam lever arm 81 formed by one arm of a bell crank 82 loosely mounted on a shaft or spindle 83. The other arm' ofthe bell crank'82 is connected by a link 84 to the temperature-setting means or pointer 2. The cam lever arm 81-is held in contact with the temperatum-adjusting cam 79 by means of a spring 85.

7 Movement of the humidity-adjusting cam 80 actuates a cam lever arm 86 forming one arm of a bell crank 87 which is also loosely mounted on the shaft or spindle 83. The bell crank 87 is connected to the humidity-setting means or pointer 3 by means of a link 88 and is held against t-he cam 80 by a spring 85'.

In the drawings, 1 have shown a construction of scale switch which I prefer to employ in conjunction with the equipment illustrated. The contacts 52' are carried in the top segment of a ring of insulating material 89, preferably made of bakelite. The contacts 54; are carried on the bottom segment of the ring 89. The movable contact'56 (conmovable element or plunger 59.

nected to the link57) is arranged to alternately engage with the contacts 52 and 54.

As the moisture content dries from. the sample 41, the arm or rod 19 moves toward,

a vertical position, and this movement is so transmitted to the contact 56 that the contacts 52 and 5a are alternately engaged. in the position as shown in the drawings, the contact '56 is in engagement with one of the contacts 52. This causes the energization of the electromagnet 53 andmovement of the As the plunger 59 moves toward the left, as shown in the drawings, in response to the energization of the elect-roinagnet 53,-the movable contact 68 sweeps past the stationary contact 69 to close the-circuit through the battery and winding 71. At the same time the cam 61 is forced to'the left by the pin 60 carried by the plunger 59, causing the spring 62 to move the switch arm 63 from idity-adjusting cam 80.

engagement with the contact 65 and into engagement with the contact 64, thus de- L energizing the windings of the electromagnet 53. When the electromagnet device 71 is energized, its plunger 72 is drawn down, causing a movement of the lever arm 73 with the resulting movement of the ratchet 77 a predetermlned prescribed amount; The movement of the ratchet 77. causes the movement of the temperature-adjusting cam 79 and humidity-adjusting cam 80 a predetermined prescribed amount. I In thismanner the temperature-setting pointer 2 is moved a predetermined prescribed amount by means of cam lever arm 81,-bell crank.

82, and link 84. Likewise, the humiditysetting pointer 3 is moved a pre-determined prescribedamount by the operationof the cam lever arm 86, bell crank 87, and link 88. It will be noted that the windings of the electromagnetic device 71 are energized only momentarily while the movable contact 68 is sweeping past the stationary contact 69.

As the moisture content of-the sample 41 2 ing cam {50 are always moved througha predetermined angle in the same direction each time the. electromagnetic device 71 is energized.

The contacts 52 and'54: are appropriately spaced in the ring 89. Preferably, the contacts 52 and 5e are uniformly spaced and the desired'conditions of temperature and humidity throughout the drying operation are secured by appropriate design of the temperature-adjusting cam 7 9'and. the hum- Diil'erent drying schedules may. be obtained by the use of cams of appropriate different design. Where the drying schedule is determined by means of thecams 7 9 and 80, the scale arm 43 does not always have to start from the same position. The scale switch (52- casing or instrument, it will be readily understood by those skilled in the art that the principles of the invention are equally applicable-to a temperature controller alone 5456) can be set according to the moisture 1,20

or a humidity controller alone, or to an independent temperature controller employed in conjunction with an independent humidity controller. In such cases the temperature-adjusting cam would be attached to the temperaturecontrolling instrument and would'be actuated in the manner described by the electromagnetic device 71; the humidity-adjusting cam would be attached to the humidity-controlling instrument and would be actuated by a similar electromagnetic device 71.

I claim 1. The combination in a drying apparatus having temperature varying means and humidity varying means and controllers" cooperating therewith for maintaining any desired conditions of temperature and humidity within the apparatus, of control means movable in response to the loss in weight of a" representative sample of the material being dried as the drying operation progresses, a pair ofielectric relay windings having temperature'varyingmeans and a controller cooperating therewith for maintaining any desired condition of temperature within the apparatus, of control means movable in response to the loss in weight of a representative sample of the material being dried as the drying operation'progresses, a pair of electric relay windings adapted to be alternately, energized by said control means, a movable member adapted to be actuated by the energization of each of said relay windings, an electromagnetic device,- means for momentarily energizing saidelectromagneticdevice each time said mov- I able member is actuated,\and means operated when said electromagnetic device is energi'zed for ad uStin saidcontroller to maintain predetermined 3. The combination in a drying apparatus having humidity varying means and a.

troller cooperating therewith for maintaining any desired condition of humidity within the apparatus, of control means movable in response to the loss in weight of a repre sentative sample of the material being dried as the drying operation -progresses, a pair mama:

V different conditions of temperature within the drying apparatus as the drying operation progresses.

'of electric relay windings adapted to be alternately energized by said control means,

a movable member adapted to be actuated by the energization of each of said relay-windings, an electromagnetic device, means for 'momentarily energizing said electromagnetic device each time said movable member is' actuated, and means operated when said electromagnetic device is energized for adjusting said controller to maintain predetermineddifierent conditions of humidity within the trying apparatus as the drying operation progressescooperating with means for maintaining determined conditions of temperature within the apparatus and humidity-setting means cooperating with means for maintaining determined conditions of humidity within the apparatus," an electromagnetic device, a lever reciprocally moved by said electromagnetic device, a member adapted to be rotated in one direction a predetermined amount by each reciprocal movement of the lever, a temperature-adjusting cam secured to said member and operatively connected with the temperature-setting means, a humidity-adjusting cam secured to said member and operatively connected with the hu- Inidity-adjusting means, means for producing an action indicative of the loss of weight 1 of a representative sample of the material being dried as the drying operation progresses, and means for actuating said'electromagnetic device in response to said ac- 'tion.

5 In an apparatus ,for drying materials which require diiferent conditions of tem-- perature and humidity during the drying operation, temperature and humidity controllers having temperatuiesetting means cooperating with means for maintaining determining conditions of temperature within the apparatus and humidity-setting means cooperatin with means for maintaining determine conditions of. humidity within the apparatus, an electromagnet device, a pivoted lever arranged to be reciprocated by the electromagnetic device, a rotatably mounted ratchet, a temperature-adjusting cam secured to the ratchet and operatively connected with the. temperature-setting means, a humidity-adjusting cam secured to the ratchet and operatively connected w'ith'the humidity-setting means, a pawl on the lever adapt d to engage and move the ratchet a predetermined amount in one direction each time the lever is reciprocated, means for producing an action indicative of the loss of weight ofa representative sample of the material being dried as the drying operation progresses, and means for actuating said electromagnetic device in response to said action.

6. In an apparatus for drying materials which require different conditions of temperature and humidity during the drying operation, temperature and humidity controllers having temperature-setting means cooperating with means for maintaining determined conditions of temperature within the apparatus and humidity-setting means cooperating with means for maintaining determined conditions of humidity within the apparatus, an electromagnetic device, means actuated by said electromagnetic device for adjusting said temperature-setting means and said humidity-settin means, means for producin an action indicative of the loss of weight 0 a representative sample of the material being dried as the drying operation progresses, a pair of electrom-a nets adapted to be energized alternately in response to said action, an electric circuit including said electromagnetic device, a stationary contact in said circuit, a movable element adapted to be reciprocated by the alternate energization of said electromagnets, and a contact on the movable element adapted to engage said stationary contact and close said electric circuit as the movable element is reciprocated.

7. In an apparatus for drying materials which require different conditions of temperature and humidity during the drying operation, temperature and humidity controllers having temperature-setting means 7 cooperating with means for maintaining reciprocated by the alternate determined conditions of temperature within the apparatus and humidity-setting means cooperating with means for maintaining determined conditions of humidity within the apparatus, an electromagnetic device, a temperature-adjusting cam operative-1y associated with the temperature-setting means, a humidity-adjusting cam operatively associated with the humidity-setting means, said temperature-adjusting cam and said humidity-adjusting cam being actuated a predetermined prescribed amount in one direction each time said electromagnetic device is energized, means for producing an action indicative of theloss of weight of a representative sample of the material being dried as the drying operation progresses,

a pair of electromagnets adapted to be energized alternately in response to said action, an electric circuit including said electromagnetic device, a stationary contact in the circuit, a movable element adapted to be energization of said ele'ctromagnets,-and a contact on the movable element adapted to engage said stationary contact and close said electric circuit as the movable'element is reciprocated.

aIn an apparatus for drying materials which require different conditions of temperature and humidity during the drying operation, temperature and humidity controllers having temperature-setting means cooperating with means for maintaining determined conditions of temperature within the apparatus and humidity-setting means cooperating with means for maintaining determined conditions of humidity within the apparatus, an electromagnetic device, a rotatably mounted shaft, a lever loosely mounted on the shaft and arranged to be actuated by the electromagnetic device, a ratchet secured to. the shaft, a temperature-adjustingcam secured to the shaft and operatively associated with the temper attire-setting means, a humidity-adjusting cluding said electromagnetic device, a stationary contact in the circuit, a movable element adapted to be reciprocated by the alternate energization of said electromagnets, and acontact on the movable'element adapt ed to engage said stationary contact and close said electric circuit as the movable element is reciprocated.

9. In an apparatus for drying materials which require different conditions of 811% perature and humidity during the drying operation, temperature and humidity con-- trollers having temperature-setting means cooperating with means for maintaining determined conditions of temperature within the apparatus and humidity-setting means cooperating with means for maiu- .taining determined conditions of humidity within the apparatus, an electromagnetic device, a rotatably mounted shaft, a lever loosely mounted on the shaft and arranged to be actuated by the electromagnetic device, a. ratchet secured to the shaft, a temperature-adjusting cam secured to the shaft and operatively associated with the temperature-setting means, a humidity-adjusting cam secured to the shaft and operatively associated with the humidity-setting means, a pawl on the lever ada ted to-engage and move the ratchet a predetermined amount in one direction each time said electromagnetic device is energized, means for producing an action indicative of the loss of weight of a representative sample of the material being dried as the drying operation progresses, and means for periodically- 1 Hill said electromagnetic device.

a lever loosely lever adapted to energizingsaid electromagnetic device in response to said. action. 'n

g In an: apparatus for drying materials which require different conditions of temperatureduring the: drying operation, atomperature controller having temperature set- I sentative sample of the material being dried.

as the, dry1ng'7'operation progresses, and means g ior' causing said action to energize IL In. an apparatus for drying materials which nire different conditions of temperatur eduringi the. drying, operation, a temperature controller having temperature-setting means: cooperatingwithv means for apparatus, an electromagnetic device, means actuated by said adapted and close said electric circuit as the movable electromagnetic device for adjusting the 0 means, means for proindicative of the loss of sample of the temperature-setti (lacing an action weightof a representative material being'dried as the be energized. alternately in readapted toaction, an electr c circuit 1n:

spouse to said i 1 eluding said electromagnetic device, a stationary contact in the circuit, a movable element adapted to alternate energization of said electromagnets, and a contact on the movable element to engage said stationary contact element is reciprocated.

12. In an which reguire different conditions of temperature within the perature uringthe drying operation, a temperature controller; having temperature-setting means cooperating with means ,for

drymg p r: ation. progresses, a pair of electromagnets.

in th a pawl on the be reciprocated by the.

apparatus for drying materials maintaining determinedconditions of temapparatus, an electromagnetic -device, means actuated by' said electromagnetic device, for adjustmg the temperaturesetting means, means for prouclng; an actiommdicative of the loss of tot a. representative sample of the material beingdried as the drying operation progresses, a pair" of. electromagnets adapted to be energized alternately in- "s onse to said actiom. anel'ectric circuit inc u ing said magnets,

uvhich require different temperature-setting means, a

a stationary contact e circuit, a movable element adapted to be moved between said pair of electromagnets, a contact on the movable element adapted toengage said stationary contact electromagnetic device,

clement moves between said pair of electroand means operated by said movable element for de-energizing that electromagnet causing movement of the movablc element.

13. In an apparatus for drying materials conditions of temperature during the drying operation, a tem- I means cooperating with means for maintaining determined conditions of temperature within the apparatus, an electroperature-adjusting cam secured to said ratchet and operatively awl on the lever adapted to engage and move] the ratchet a predetermined amount rection each time said electromagnetic device is energized, means for producing an action indicative of the loss of weight of a representative sample of the material being dried as the drying operation progresses, and means for causing said action to energize said electromagnetic device.

tive sample of the material being dried as the drying operation v a horizontally pivoted balance hold a representativ terial being dried, balance and-connected thereto by a flexible member whereby movement of the balance arm is transmitted to the rod, 2. series of stationary electrical'contacts, a switch arm to engage the electrical contacts, and a connection between the rod and the switch arm for transmitting movements of the rod to the switch arm.

15. In an apparatus for drying materials which require different conditions of humidity duringthe drying operation, a humidity controller having humidity-setting means cooperating with means for maintaining determined conditions of humidity within the apparatus, anelectromagnetic device, a rotatably mounted shaft, a lever loosely mounted on the shaft and arranged to be actuated by the electromagnetic device, a ratchet secured to the shaft, a humidityadjusting cam secured to the shaft and 0peratively associated with the humidity-set ting means, a pawl on the lever adapted to engage and move the ratchet a predeter mined amount in one direction each time in one dia rod pivoted above the indicative of the said electromagnetic device is energized, means for producin an action indicative of the loss of weight 0 a representative sample of the material being dried as the drying operation progresses, and means for causing said action to energize said electromagnetic device.

16. In an apparatus for drying materials which require different conditions of humidity during the drying operation, a humidity controller having humidity-setting means, cooperating with means for maintaining determined conditions of humidity within the apparatus, an electromagnetic device, means actuated by said electromagnetic device for adjusting the humidity-setting means, means for producing an action loss of weight of a representative sample of the material being dried as the drying operation progresses, a pair of electromagnets adapted to beenergized alternately in response to said action, trio circuit including said electromagnetic device, a stationary contact in the circuit. a movable element adapted to be moved by each of-said eleotroma-gnets, and a contact on. the movable element adapted to engage said stationary contact and close said electric circuit when the movable element is movedby either of said electromagnets.

17 In an apparatus for drying materials which require different conditions of humidity during the drying operation, a humidity controller having humidity-setting means cooperating with means for maintaining determined conditions of humidity within the apparatus, an electromagnetic device,

means actuated by said electromagnetic device for adjusting the humidity-setting means, means for roducing an action indicative of the loss 0? an elec' -v1ce, a lever arranged to be'reciprocally said electromagnetic devlce, a

weight of a representative sample of the material being dried as the drying operation progresses, a pair of electromagnets adapted to be energized a1- ternately in response to said action, an electric circuit including said electromagnetic device, a stationary contact in the cirguit, a movable element adapted to be moved tli e movable element adapted to engage said stationary contact and close said electric circuit when the movable element is moved by either, of'said electromagnets, and means op- --erated by said movable element for de-energizing that electromagnet causing movement of the movable element.

18. In an apparatus for drying materials which require difi'erent conditions of humidity during thedrying operation, a humidity controller having humidity-setting means cooperating withmeans for maintaining determined conditions of humidity within the apparatus, an electromagnetic demoved by rotatably mounted ratchet, a humidity-adjusting cam secured to said ratchet and oporatively associated with the humidity-setting means, a pawl on the lever adapted to engage and move the ratchet a predetermined amount in one direction each time said electromagnetic device is energized, means for producing an action indicative of the loss of weight of a. representative sample of the material being dried as the drying operation progresses, and means for causing each of said electromagnets, a contact on said action to energize said electromagnetic 1 device. 7 In testimony whereof I affix mysignatuIB. y.

f JOHN BERCHMANS WELCH.

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