US3451662A - Batch drier for grain - Google Patents

Batch drier for grain Download PDF

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Publication number
US3451662A
US3451662A US644655A US3451662DA US3451662A US 3451662 A US3451662 A US 3451662A US 644655 A US644655 A US 644655A US 3451662D A US3451662D A US 3451662DA US 3451662 A US3451662 A US 3451662A
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United States
Prior art keywords
grain
temperature
relay
contact
drying
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Expired - Lifetime
Application number
US644655A
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English (en)
Inventor
Stephen Frederic Burghard
John Herbert Wyndham Wilder
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JOHN WILDER Ltd
WILDER Ltd JOHN
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WILDER Ltd JOHN
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Publication date
Priority claimed from GB2598266A external-priority patent/GB1148938A/en
Application filed by WILDER Ltd JOHN filed Critical WILDER Ltd JOHN
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    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F26—DRYING
    • F26B—DRYING SOLID MATERIALS OR OBJECTS BY REMOVING LIQUID THEREFROM
    • F26B21/00—Arrangements or duct systems, e.g. in combination with pallet boxes, for supplying and controlling air or gases for drying solid materials or objects
    • F26B21/06—Controlling, e.g. regulating, parameters of gas supply
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F26—DRYING
    • F26B—DRYING SOLID MATERIALS OR OBJECTS BY REMOVING LIQUID THEREFROM
    • F26B25/00—Details of general application not covered by group F26B21/00 or F26B23/00
    • F26B25/001—Handling, e.g. loading or unloading arrangements
    • F26B25/002—Handling, e.g. loading or unloading arrangements for bulk goods

Definitions

  • This invention relates to a drier for grain and similar commodities, which is preferably a batch drier, that is to say, a drier which operates on batches of the commodity in turn rather than one which acts continuously to dry a commodity moving in a continuous path.
  • the temperature of the drying air being supplied to the grain is maintained reasonably constant at a predetermined temperature, then the temperature of the air leaving the grain is a measure of the dryness achieved and does in fact affect an averaging of the dryness of the whole content of the batch so that one does not have to measure the dryness at different samples throughout the batch.
  • a cooling operation may be automatically initiated and this too can continue until a thermal responsive device indicates that the grain is sufficiently cool, so that the batch of grain can be removed from the drier and automatic re-cycling can commence by refilling with a fresh load of wet grain.
  • thermoelectric device for shutting down the burner if the temperature of the air passing to the drier exceeds some predetermined temperature, for example, F. above which the grain would be damaged.
  • a certain dryness of the dried grain corresponds with a temperature of the air leaving the drying zone which is greater for grains which contain more moisture before drying. Assuming that grain is required to be dried to 16% moisture content, if it contains 20% moisture before drying, the temperature of the air leaving the drying area when the grain contains 16% moisture might be 92 F., whereas the temperature for the same dryness might be 93 R, if the grain contained 24% moisture before drying. In general, the wetter the grain before drying the higher will be the temperature of the drying air leaving the drying area when the desired degree of dryness has been achieved.
  • the operator does not have to make any adjustment but merely fills the hopper with the grain to be dried and, as the drying operation proceeds, the device automatically resets the reference temperature upwards, either in steps or continuously.
  • the temperature of the air leaving the drying area will increase as the grain become drier, and in general it will increase at a faster rate than the rate of increase of the reference temperature until the time it has overtaken the reference temperature, at which time a signal is given to terminate the drying operation.
  • the reference temperature may be arranged to remain constant after a certain time, or even be progressively reduced after a time.
  • the initial reference temperature may be set dependent upon the desired dryness to be achieved.
  • a farmer may want to dry his grain to have 16% of water or perhaps 15% of water depending upon whether the grain is to be sold immediately or is to be stored before sale and this he can do by selecting the initial reference temperature.
  • the higher he sets the initial reference temperature the longer will it take for the outlet air temperature to overtake the increasing reference temperature and so the longer will be the drying period and the greater the degree of dryness achieved.
  • Seed for example, in general requires to be dried more slowly than grain if the seed is still to remain capable of germination and this can be achieved by use of this control. The same dryness can be achieved in the same Way, but it can be arranged to take longer.
  • the temperature responsive device is arranged to give successive electrical signals as the temperature measured increases through discrete steps and the device is arranged to generate successive electrical signals corresponding to increasing reference temperatures and a simple circuit can make a comparison and give a signal when the measured temperature has overtaken the reference temperature.
  • Balance can be detected by means of an electrical bridge having resistances responsive respectively to (a) the temperature being measured, (b) the changing reference temperature, (c) a fixed value, and (d) an adjustable value for calibration purposes.
  • One pulsing device which may be used has a small mercury switch which is driven to and fro by a geareddown motor, the mercury making with a contact at one endof its glass bulb each time the switch reaches the end of its travel.
  • a system of this kind can be arranged to generate pulses at frequencies from a few seconds to a substantial part of an hour.
  • FIGURE 3 shows a modification of the circuit diagram
  • FIGURE 4 shows an alternative control arrangement.
  • the compartment for each batch of grain to be dried is of generally annular constant cross-section along a horizontal axis and may be defined as the space between expanded metal inner and outer hexagonal shaped casings 11 and 12, and closed ends.
  • Grain is fed into the compartment from a hopper 13 at one end by means of a screw feed 14 driven by an electric motor for taking the grain from the hopper towards the other end of the casing.
  • a fan 15 at one end of the interior of the inner casing 11 draws drying or cooling air through the grain in generally 4 radial directions from an enclosure surrounding the outer hexagonal casing 12.
  • This enclosure 16 defines a distribution space for the air which enters at the lower part of one end of the enclosure through a chamber 17 by way of a burner 18 which might burn gas or oil, or might be electric.
  • the batch drier is thus enclosed and operates by radially inwardly flowing hot air through the grain.
  • a second screw feed 19 is used for removing a batch of dried grain in preparation for receipt of the next wet batch at the top and this feed 19 is also driven by an electric motor.
  • FIGURE 1 also shows a top pressure switch H mounted at the far end of the feed 14 which operates to close an electric contact in the circuit of FIGURE 2 when the grain rises sufiiciently indicating that the drying chamber is full.
  • a bottom pressure switch I which also has a contact in the control circuit which is closed about half way through the filling operation and which opens again when all the grain has been removed and the drier is ready for the next batch of wet grain.
  • T1 and T2 are clocks which can be pre-set to any desired time interval and which each have two contacts which close in turn with an interval of about five minutes, the first one closing after the clock has run for the preset time.
  • the clocks run as long as an electrical supply is maintained through their motors both contacts of a clock return to the normal positions when the electrical supply is removed from an energising winding F associated with that clock. The clocks are then ready for a new cycle when the windings F are again energised. It is to be noted that the clocks remember the pre-set time from cycle to cycle and do not have to be set each time as with an egg-timer type of clock.
  • the relays A and C are for operating the loading and unloading motors driving the feeds 14 and 19, while the relay B is used to switch on the fan 15 for inducing the flow of hot and cold air through the grain.
  • T4 is a hand operated clock which can be set to prevent refilling of the drier after a set time, perhaps because the supply of grain will be exhausted by that time or because only a certain number of loads are to be dried.
  • the operation of drying a batch may be summarised as follows: After filling the drying compartment the grain is dried for about 2 hours using air at a temperature of about F. This is followed by drawing cooling air through the grain but with the burner not operating, for 15 to 20 minutes after which the unloading feed starts to empty the drier at the end of that cycle. It should be explained that these temperatures and times are examples suitable for particular grain in a particular state and experience will determine the setting in a particular case.
  • Initiation of automatic operation is by hand operation of three switches W, X, and Y so that the contacts W X Y in series are all closed to connect the control circuit supply from the mains line L to the contacts of the switches H and J and to the relay A of the loading motor through the normally-closed contacts T T B and C
  • the main switch S for the loading motor is closed to start the loading motor so that the grain is fed from the hopper 13 through the loading feed 14 into the drying compartment.
  • Closing of the switch W ensures that a switch W for hand operation of the loading motor remains open, and similarly, closing of the switch contacts X and Y ensures that contacts X and Y remain open to prevent hand operation of the fan motor and the unloading motor.
  • a contact X closes at the same time to enable the fan motor relay B to be energised when the supply becomes available.
  • the relay A Once the relay A has operated, its contact A closes to short circuit the normally closed contact T 1 of the clock T Thus the clock can only prevent starting of a filling operation and cannot stop it once it has started. Its contact can also be shorted by a hand-operated contact V. Also the contact A opens to ensure that the relay C for the unloading motor cannot become energised when the switch I closes.
  • the switch H closes to energise through the contacts T No. 2 and X the relay B for the fan motor, and in consequence the fan motor switch S closes.
  • the contact B opens to de-energise the relay A so that the loading motor stops and the contact B closes to maintain the supply across the relay B in spite of any opening of the switch F for example due to the grain level falling as the grain is dried.
  • the contact B opens to maintain the relay C tie-energised in spite of closing of the relay contact A and the contact B closes to provide the supply for the burner 11 which ignites provided a manual switch Z has been closed, so that the hot air is delivered to the fan through the grain in the drying chamber. This state of affairs continues until a temperature responsive device detects that drying has been completed.
  • the temperature responsive device is situated within a discharge duct 20 (FIGURE 1) leading from the fan 15 to be responsive to the temperature of the air leaving the drying compartment. It may be considered to operate to close a contact S in series With the relay R in the circuit of FIGURE 2 when a preset temperature is achieved.
  • the relay R has four contacts. The first contact R is a normally closed contact in series with the normally-closed contact C for preventing operation of the filling relay A when the relay R is operated.
  • a self-holding contact R closes when the relay R is energised to hold it in, a normally-open contact R closes to start the cooling timing clock T when the relay R is energised, and a normallyclosed contact R de-energises the burner E once the detection of the correct temperature has indicated that the grain is dry.
  • a manual switch has a contact U which when open isolates the common contact of the switch T 2 from the supply and also isolates the clutch coil F of the clock T and an alternative contact U which when closed completes an energisation path for the relay R provided the switch S is closed.
  • the drying time is determined by a preset clock T
  • the fan continues to run until at the end of the cooling time the contact T N0. 1 opens (to prevent subsequent energisation of the relay A when the relay B is released) and five minutes after this the contact T N0. 2 opens to remove the supply from the relay B and stop the fan.
  • the contact B closes so that now the relay C is energised through the switch I and the contacts A and B This starts the unloading motor through its main switch S and the dried and cooled grain is unloaded from the drier until when it is empty the switch I switches back to the position shown in FIGURE 2 and the relay C is released.
  • the contact C is open to prevent re-energisation of the relay A and when the switch I opens the energising supply is removed from the winding F of the clock, T so that its contacts T N0. 1 and T N0. 2 are in the position shown in FIGURE 2. in preparation for the next cycle which begins again automatically as soon as the contacts T N0. 1, B and C are all once again closed.
  • FIGURE 2 For this purpose the circuit of FIGURE 2 is modified as shown in FIGURE 3. The modifications only concern the connection to the relay R and in other respects the circuit is similar.
  • a relay Q has a normally-closed contact Q1 for energising the relay R, when the relay Q is released, to terminate the drying operation and commence the cooling operation timed by the clock
  • a control circuit for the relay Q includes a temperature responsive potentiometer 31 which is arranged automatically to increase in resistance over a set range for a selected increase of temperature in the range 5 F. to 22 F.
  • This temperature responsive device 31 is connected in a bridge arrangement with two equal resistors 32 and 33 and a control potentiometer 34 having a wiper which can be driven in steps by a motor 35 to be progressively increased or decreased in dependence on the setting of the contact P1 of a timer P.
  • the resistance of the temperature responsive device 31 will be lower than the resistance of the potentiometer 34 so that the bridge will be unbalanced and a relay N connected across one diagonal will be energised, and its normally-open contact N in series with the relay Q and the supply will be closed to energise the relay Q and hold the contact Q1 open.
  • the contact B closes to energise a pulser 36 and a timer P.
  • the timer P runs for a predetermined time for a purpose which will be described below.
  • the pulser 36 can be set by means of dials 37 and 38 to emit operating pulses for the motor 35 with a duration which can be set by the knob 37 and an interval between pulses which can 'be set by the knob 38. Both pulse duration and pulse interval can be varied between 1 and 57 seconds.
  • the contact R disconnects the output of the pulser 36 from the motor 35 and the contact R closes to provide continuous energisation of the motor 35 to reset it to its lowest value ready for the next batch of gram.
  • the temperature of the air leaving the drying chamber at which termination occurs increases progressively from perhaps 80 F. to 100 F. over a time (for example 1 hour) which can be selected by adjustment of the pulser 36 and adjustment of the differential of the temperature responsive potentiometer 31. After a time, further increase of the termination temperature is not required, and for some grains it may be required to drop progressively after a time.
  • the resistance of the potentiometer 34 can be kept constant or can be arranged to be driven in the re verse direction. This is effected merely by opening or changing over the contact P which causes the pulses from the pulser 36 to cease to be effective, or to act in the reverse direction, in accordance with the characteristic desired. Eventually, when the bridge becomes balanced, the drying operation will be terminated.
  • drying air entering the drying chamber is at a constant known temperature.
  • thermometer 41 having a number of electrical contact wires 42 sealed into the glass tube for the mercury so that as the mercury rises it will make contact with the wires in turn.
  • the wires 42 are connected to an electronic switching circuit 43 operated in steps by the pulser 36 so that the different wires 42 are connected in turn in series in a circuit including the relay Q whose single contact is a normally-open contact in series with the relay R in the circuit of FIGURES 2 and 3.
  • the relay Q operates to terminate the drying operation by energising the relay R.
  • a grain drier including means for passing heated air at a predetermined temperature through the grain for drying it, and a device arranged to measure the temperature of the air after leaving the grain and means responsive to the temperature of the air leaving the grain rising to a certain temperature for terminating the drying operations and initiating a further operation on the grain.
  • a drier as claimed in claim 1 including a device for setting a reference temperature and means for resetting the reference temperature automatically in response to increased duration of the drying operation of a drying cycle, in which the responsive means terminates the drying operation when the temperature of the air leaving the grain reaches the reference temperature.
  • a device as claimed in claim 3 in which the reference temperature is arranged to stop increasing after a predetermined time, and to remain constant or to decrease progressively.
  • a batch grain drier as claimed in claim 1 including means for automatically loading the drier, drying the grain and unloading the drier in a drying cycle in response to the temperature responsive means, and for automatically recycling.
  • a drier as claimed in claim 1 including means for maintaining the heated air for drying the grain at a constant temperature related to the said certain temperature.
  • a drier as claimed in claim 6 including a burner for heating the air, which burner has two jets for burning fuel one of which operates continuously and the second of which is switched on and oit in dependence on a thermometer measuring the temperature of the air passing to the grain.
  • thermometer 8. A drier as claimed in claim 1 in which the temperature measuring device comprises a variable resistance thermometer.
  • a drier as claimed in claim 1 including a variable resistance thermometer for measuring the temperature of the air leaving the grain in which the variable resistance element of the thermometer is connected in an elec- 9 trical bridge arrangement which is arranged to be balanced when the resistance of the thermometer is equal to the resistance of another component of thebridge which is arranged to be progressively reset.
  • a drier as claimed in claim 2 including means for adjusting the rate of resetting of the reference temperature.

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  • Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • General Engineering & Computer Science (AREA)
  • Drying Of Solid Materials (AREA)
US644655A 1966-06-10 1967-06-08 Batch drier for grain Expired - Lifetime US3451662A (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
GB2598266A GB1148938A (en) 1966-06-10 1966-06-10 Batch drier for grain
GB5443066 1966-12-05

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DE (1) DE1729505A1 (de)

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4076492A (en) * 1976-12-27 1978-02-28 Afe Industries, Inc. Electronic dryer

Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2991559A (en) * 1957-10-16 1961-07-11 Harold W Pierpoint Grain drier
US3053522A (en) * 1957-10-11 1962-09-11 Robert D Applegate Continuous drier
US3056214A (en) * 1957-07-10 1962-10-02 Jr Arthur Andersen Portable batch type dryer
US3092472A (en) * 1959-11-23 1963-06-04 Charles D Figley Grain drier
US3203679A (en) * 1960-10-17 1965-08-31 Whirlpool Co Automatic control of plural heaters in a clothes drier
US3404467A (en) * 1965-12-20 1968-10-08 Burghard Stephen Frederic Batch drier for grain

Patent Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3056214A (en) * 1957-07-10 1962-10-02 Jr Arthur Andersen Portable batch type dryer
US3053522A (en) * 1957-10-11 1962-09-11 Robert D Applegate Continuous drier
US2991559A (en) * 1957-10-16 1961-07-11 Harold W Pierpoint Grain drier
US3092472A (en) * 1959-11-23 1963-06-04 Charles D Figley Grain drier
US3203679A (en) * 1960-10-17 1965-08-31 Whirlpool Co Automatic control of plural heaters in a clothes drier
US3404467A (en) * 1965-12-20 1968-10-08 Burghard Stephen Frederic Batch drier for grain

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4076492A (en) * 1976-12-27 1978-02-28 Afe Industries, Inc. Electronic dryer

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DE1729505A1 (de) 1971-06-24

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