US3404467A - Batch drier for grain - Google Patents

Description

S. F. BURGHARD BATCH DRIER FOR GRAIN Oct. 8, 1968 2 Sheets-Sheet 1.

Filed Dec. 20, 1966 INVENTOR STEPHEN FT Buaemuzb BY wataw cbee, 4 W137) ATTORNEYS Oct. 8, 1968 U H D 3,404,467

BATCH DRIER FOR GRAIN Filed Dec. 20, 1966 2 Sheets-Sheet 2 --1 B l w- 1 C INVENTOR STEPHEN F. BURGHARD.

mzwpwea, ATTORNEY United States Patent 3,404,467 BATCH DRIER FOR GRAIN Stephen Frederic Burghard, The Mill House, Wakes Colne, near Colchester, Essex, England Filed Dec. 20, 1966, Ser. No. 603,233 Claims priority, application Great Britain, Dec. 20, 1965, 53,844/ 65 13 Claims. (Cl. 34--56) ABSTRACT OF THE DISCLOSURE A batch drier for grain is disclosed which includes an annular drying chamber into which grain is fed for drying and subsequently removed. Surrounding the chamber is an external enclosure with a duct located radially inwardly of the drying chamber through which drying and cooling air is drawn. Automatic control means regulates the loading, drying and unloading operations according to a predetermined sequence.

This invention relates to a batch drier for grain and similar commodities, 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.

According to the present invention a batch dried includes means for automatically loading the drier, drying the grain, and unloading the drier, in a drying cycle, and for automatically re-cycling. The drying cycle may also include the step of automatically cooling the dried grain before unloading.

The automatic initiation of a new cycle when the grain has been unloaded from the drier following a preceding cycle enables batch drying to be carried out continuously Without the necessity of having an operator looking after the machine all the time.

There could be one or two timing clocks which can be set respectively to a convenient drying time and a convenient cooling time, but as an alternative a device sensitive to the wetness of the grain and a device sensitive to the temperature of the grain could be used to indicate when drying is complete and when cooling has been achieved respectively.

Automatically operated filling mechanism for filling the drying compartment from a supply of grain could operate in association with a switch at the top of the drying compartment for indicating when the compartment is full and switching off the filling mechanism. Similarly automatically operating emptying mechanism could be associated with a switch which operates when the compartment is empty to switch off the emptying mechanism.

The drier itself conveniently operates by radially inward flow of drying air or cooling air through the grain and this flow of air is conveniently achieved by suction from within the grain compartment rather than by blowing from without.

Thus in a preferred form of the drier the drying chamber is generally of annular form whether horizontal or vertical and the air is drawn radially inwards through the perforated walls of the annular chamber into a central 7 area under the influence of a fan providing the necessary Patentedl Oct. 8, 1968 of example with reference to the accompanying drawings of which:

FIGURE 1 is a sketch showing the general arrangement of a batch drier housing embodying the invention; and

FIGURE 2 is a circuit diagram of the control system.

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 easing. A fan 15 at one end of the interior of the inner casing 11 draws drying or cooling air through the grain in generally 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 radial- 1y inwardly flowing hot air through the grain. At the lower part of the grain compartment between the casings 11 and 12 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.

The relays for switching the motors on and off are shown at A and C in the control circuit of FIGURE 2 the relay A being for the motor for the feed 14 for supplying moist grain and the relay C being for the motor driving the feed 19 for removing the dried grain.

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. Similarly there is 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.

The automatic recycling operation of the batch drier will be understood best from the description of operation of the control circuit in FIGURE 2.

T and T are clocks which can be preset 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 pre-set 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 burner 18 in FIGURE 1 has a control shown at E in FIGURE 2 and this control includes a circuit for energizing a lock-out relay D whenever a photo-electric device detects that the burner has gone out and the air is no longer being heated. For the purposes of this description it is sufficient to say that the burner operates whenever there is an external connection between the terminals marked 8 and 6 on the control E.

As has been described above the relays A and C are for operatin 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. T is a hand operated clock which canbe 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 140 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 settin in a particular case.

The operation of the automatic control system will now be described and it is believed that the nature of the control circuit shown in FIGURE 2 will become apparent from this description without its being first described in detail.

It will be noticed that at starting the switches H and I will be in the open position shown in FIGURE 2 so that there will be no supply to the relay B for energising the fan motor and no supply to the energising windings F of the clocks T and T and also no supply to the relay C for the unloading motor.

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 main 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 In consequence 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.

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.

Loading continues until when the drier is about half full of grain the switch I closes to provide the energising supply to the winding F of the clock T However, the relay C is not energised because the contact A is open.

Eventually when the drier is full, the switch H closes to energise the winding F of the clock T and in fact to start the clock motor through the normally closed contacts T N0. 2, T N0. 2 and D The supply voltage is also supplied through the contacts T N0. 2 and X to energise the relay B for the fan motor and in consequence the fan motor switch S closes. The contact B opens to deenergise 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 H for example due to the grain level falling as the grain is dried. The contact B opens to maintain the relay C de-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 the. time of about two hours set on the clock T has expired. It should be noted that if the fiame goes out accidentally the photoelectric detector will energise the relay D so that the contact D will open and stop the motor of the clock T until re-ignition has occurred.

At the end of the time set on the clock T the contact T N0. 1 opens to switch off the burner 11 so that the air drawn through the grain by the fan 15 ceases to be heated and can now be used to cool the grain. Five minutes after this the contact T N0. 2 changes over to start the motor of the clock T which is set to the desired cooling time.

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 and to remove the energising supply from the winding F of the clock T so that the contacts T Nos. 1 and 2 switch back to the positions shown in FIGURE 2. Release of the relay B causes the contact B to close although the relay A is not re-energised because the contact T N0. 1 is now open. The contact B opens and also the contact B to prevent re-ignition of the burner 11 in consequence of the closing of the contact T N0. 1.

Also 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. During operation of the unloading motor 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.

Each of the main switches S S and S has an overload coil in each phase capable of operating an overload trip which in the conventional use of a direct-on-line starter would operate to open a contact in the circuit of the operating relay A, B or C. However, in the present circuit the overload trip contacts 5A 8B SC are connected in series in the supply to the control circuit so that if any one of the motors is overloaded the control circuit is de-energised and everything shuts down.

In practice one can estimate from experience the control time to be allowed for drying and cooling but in a. modification either of the clocks T and T can be dispensed with by using devices respectively sensitive to the wetness of the grain and the temperature of the grain. Thus instead of having the clock T one could have a wetness device which would detect when the grain was dried and operate contacts equivalent to the contacts T N0. 1 and T N0. 2 and in the same way a temperature device could be used instead of the clock T having contacts which open when the grain is cooled after the drying operation.

Such a device might measure repeatedly the wetness of small samples of the grain until a measurement showed that the grain was sufficiently dry. In order to avoid a false reading due to a small random sample being drier than the bulk of the grain, it could be arranged that a dryness reading must be repeated or must persist for some minutes before the drying operation is concluded.

The filling and emptying arrangements could each be at either end of the drier, and of course the disposition and operation of the switches H and I will depend upon the arrangement chosen.

What I claim as my invention and desire to secure by Letters Patent is:

1. A batch drier for grain comprising a drying chainber of annular form, means for loading grain into said chamber, means for emptying grain from said chamber, an external enclosure defining a distribution space for air around the chamber, a duct radially inwardly of the drying chamber, means for drawing drying and cooling air radially inwardly through the duct from the distribution space, and automatic cycling means for controlling the loading and emptying means and the means for drawing air in a predetermined sequence including the steps of loading, drying, unloading and recycling said steps.

2. A batch drier as claimed in claim 1 including means for automatically cooling the dried grain before unloading.

3. A batch drier as claimed in claim 1 including a timing clock which can be set to a repeatable predetermined drying time.

4. A batch drier as claimed in claim 1 including a device sensitive to the wetness of the grain for controlling termination of the drying step.

5. A batch drier as claimed in claim 1 including a device sensitive to the temperature of the grain for controlling a step in the cycle.

6. A batch drier as claimed in claim 2 including a device sensitive to the temperature of the grain for controlling the termination 01": the cooling step.

7. A batch drier as claimed in claim 1 including a switch at the top of the drying chamber responsive when the compartment is full to switch off the loading means.

8. A batch drier as claimed in claim 1 including a switch responsive when the drying compartment is empty to switch off the emptying means.

9. A batch drier as claimed in claim 1 wherein said means for drawing air comprises a fan located in a region radially within the drying chamber.

10. A batch drier as claimed in claim 1 including means for rendering the loading device inoperative after a drying step has started and before the unloading step has ended.

11. A batch drier as claimed in claim 1 in which the drying chamber has perforated walls.

12. A batch drier as claimed in claim 11 including inner and outer perforated walls defining the drying chamber, the radius of the inner perforated wall from the axis of the chamber being greater than the radial distance between the inner and outer walls.

13. A batch drier as claimed in claim 1 including a heater for raising the drying and cooling air to a predetermined temperature.

References Cited UNITED STATES PATENTS 2,733,521 2/1956 Zollman 34-174 XR 3,000,110 9/1961 Forth et a1. 34--174 XR 3,056,214 10/1962 Andersen 34-174 XR 3,057,080 10/1962 Haddix 34-474 3,092,472 6/1963 Figley 34-174 XR KENNETH W. SPRAGUE, Primary Examiner.

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