Classifications

• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F26—DRYING
  • F26B—DRYING SOLID MATERIALS OR OBJECTS BY REMOVING LIQUID THEREFROM
  • F26B15/00—Machines or apparatus for drying objects with progressive movement; Machines or apparatus with progressive movement for drying batches of material in compact form
  • F26B15/10—Machines or apparatus for drying objects with progressive movement; Machines or apparatus with progressive movement for drying batches of material in compact form with movement in a path composed of one or more straight lines, e.g. compound, the movement being in alternate horizontal and vertical directions
  • F26B15/12—Machines or apparatus for drying objects with progressive movement; Machines or apparatus with progressive movement for drying batches of material in compact form with movement in a path composed of one or more straight lines, e.g. compound, the movement being in alternate horizontal and vertical directions the lines being all horizontal or slightly inclined
  • F26B15/16—Machines or apparatus for drying objects with progressive movement; Machines or apparatus with progressive movement for drying batches of material in compact form with movement in a path composed of one or more straight lines, e.g. compound, the movement being in alternate horizontal and vertical directions the lines being all horizontal or slightly inclined the objects or batches of materials being carried by wheeled trucks
• • 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
  • F26B25/22—Controlling the drying process in dependence on liquid content of solid materials or objects
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F26—DRYING
  • F26B—DRYING SOLID MATERIALS OR OBJECTS BY REMOVING LIQUID THEREFROM
  • F26B2210/00—Drying processes and machines for solid objects characterised by the specific requirements of the drying good
  • F26B2210/16—Wood, e.g. lumber, timber

Definitions

• the present invention concerns a procedure for controlling the operation of a drive-through chamber type timber drying kiln in which the timber loads to be dried are conveyed on a roller track or equivalent through a front door into a drying channel and from which the timber loads are after drying removed on the opposite side of the drying kiln through a back door, and in which two or more independently operating drying chambers have been connected in series so that when the timber loads are transferred from a preceding chamber to the next chamber, the drying process is continued in this chamber substantially onward from that point in the drying schedule which was reached in the preceding chamber.
• So-called drive-through chamber type drying kilns are known in prior art.
• the structure of these is such that drying kiln loads assembled of drying kiln packages are conveyed into a drying chamber on a roller track in front of them, whence the loads are pushed into the drying kiln chamber.
• the dried loads are taken out through the opposite door of the drying kiln chamber.
• These chamber-type drying kilns of prior art have the advantage that in them the load-changing time is relatively short.
• a drawback is, however, the expensive implementation of such drying kilns, because they require two opposed doors and roller tracks on both sides of the drying kiln chamber.
• This control arrangement known in the art involves the drawback that when the load to be dried is moved from one chamber to another the controller of this chamber must be re-programmed every time to conform to the drying schedule of each incoming load. This causes great need of programming, and/or the procedure leads to complicated and expensive control means.
• the object of the present invention is to avoid the drawbacks mentioned and to produce a new and a more advantageous control system in drive-through chamber type drying kilns.
• the invention is mainly characterized in that to control the operation of a group of drying kiln channels connected mutually in series has been provided a control system having as many control units as there are drying kiln chambers in said drying kiln chamber assembly, and
• control signal of said control unit is disposed to follow along with said timber load to be dried and to become connected in each instance to the controls or equivalent of that drying chamber in which the particular package to be dried resides at each moment.
• Fig. 1 presents in a schematical drawing, a drive-through chamber type drying kiln and the control system according to the invention controlling its operation.
• Fig. 2 shows the principle of the programme cycle selector switch belonging to the control system of the invention.
• Fig. 3 presents a principle example of a possible drying schedule to be followed in the drying kiln of the invention.
• the chamber-type drying kiln comprises three series-connected drive-through chamber-type drying kilns K 1 ,K 2 and
• K 2 and K 3 has a common front door 11, wherethrough the timber loads
• P 2 and P 3 pass through the drying chambers K 1 , K 2 and K 3 on their carts 15, the wheels 16 of which move on tracks 10 passing through the group of chambers. Between the drying chambers are placed movable partitions 12 and 13, which may be of rather low-weight construction.
• Fig. 1 are schematically shown the air circulation means by which the drying air is circulated in each chamber K through the timber package P to be dried, the temperature and/or humidity of this air being controlled by a control system according to the invention connected to the drying kiln.
• the said means for circulating the drying air have been quite schematically depicted in Fig. 1 and regarding a more detailed embodiment example reference is made to the Finnish patent application No. 831331 by the same applicant.
• On one side of and/or above each drying chamber K is disposed an air circulation duct 17, defined, as shown in Fig. 1, by a partition 18 and an upper wall 19.
• a blower 20 on the suction side of which intake air ducts 21 open into the channels 17 and through which fresh air (arrow F in ) is drawn to the drying air circulation.
• intake air ducts 21 open into the channels 17 and through which fresh air (arrow F in ) is drawn to the drying air circulation.
• exhaust air ducts not depicted.
• drying air heating radiators 25 the volumetric flow and/or temperature of the heating fluid circulating in them being controlled with a control valve 24.
• control dampers 22 in the intake air ducts 21 is controlled by control motors 23.
• control valve 24 of the heating radiator 25 is controlled with control motors 26.
• Each drying chamber K 1 ,K 2 and K 3 is provided with control means of its own for the intake air and drying air heating radiator 25.
• control system controlling the operation of the chamber-type drying kiln according to the invention depicted in Fig. 1, said control system comprising three separate control centres S 1 , S 2 and S 3 .
• the control centres S provide, in accordance with a programme entered in them in each instance in a manner known in itself in the art, a control signal a 1 ,a 2 and a 3 .
• Said control signals a 1 ,a 2 and a 3 are connected to a programme cycle selector switch means 30 which directs the control signals a 1 ,a 2 and a 3 each in turn to control the operation of the control motors 23,26 of the different chambers K 1 ,K 2 and K 3 of the drying kiln.
• the control system may, if required, include measuring means and feedback means, by which for instance the state of the drying air circulating in the different drying chambers K 1 ,K 2 ,K 3 is monitored and the control signals a 1 , a 2 and a 3 are accordingly influenced.
• the control signals a 1 ,a 2 ,a 3 may also be formed according to the "blind control" principle, in which case said measuring means and feedback arrangements are not needed.
• the straight line K represents the dry temperature t k of the drying air and the straight line M, the equivalent wet temperature t m .
• the horizontal axis T is the drying time and the vertical axis t, said drying air temperatures t k and t m in oC.
• the switch 31 of the selector means 30 is turned, or automatically caused to turn, so that the control signal a 1 now goes along with the timber package P 1 , that is, the control signal a, coming from the first control centre S 1 begins to control the operation of the second chamber K 2 with the aid of its control motors 23 and 26. It is thus understood that the drying process is continued following the drying schedules K and M in the second chamber K 2 as if no transfer had taken place regarding drying schedule and directing of the control means.
• the timber package P 1 has been moved from the first chamber K 1 to the second chamber K 2 and a new package has been introduced in the first chamber K 1 , and the control of this latter package's drying process is taken up, as shown in Fig. 2, by the control centre S 3 , which has just been released from controlling the drying of the package P 3 removed from the last chamber K 3 , the drying schedule implied by the new package having been programmed in the control centre S 3 .
• the drying process is carried out, as shown in Fig. 3, during the interval T 2 -T 1 to the dry temperature t 2k and the wet temperature t 2m , whereafter the package is moved to the next drying chamber K 3 and at the same time the selector switch 31 is stepped to its next position, in which the control signal a 1 of the control centre S 1 is directed to act on the control motors 23 and 26 of the third chamber K 3.
• drying of the same package is carried out during the interval T 3 -T 2 to the ultimate dry temperature t 3k and wet temperature t 3m under control by the same control centre S 1 under the control of which the drying process was commenced in the first chamber K 1 and carried out also in the second chamber K 2 .
• drying kilns in actual practice there are as a rule several drying kiln chamber groups K 1 - K N connected parallel. Each drying kiln chamber group K 1 - K N then has its own control system with as many (N) independently acting control units S 1 -S N as there are consecutive drying kiln chambers connected in series in the drying kiln chamber group controlled by it.

Landscapes

• Engineering & Computer Science (AREA)
• Mechanical Engineering (AREA)
• General Engineering & Computer Science (AREA)
• Drying Of Solid Materials (AREA)

Priority Applications (3)

Applications Claiming Priority (2)

Publications (1)

Family

ID=8518075

Family Applications (1)

Country Status (4)

Cited By (18)

Families Citing this family (2)

Citations (4)

Family Cites Families (1)

• 1983
  • 1983-11-15 FI FI834185A patent/FI78348C/fi not_active IP Right Cessation
• 1984
  • 1984-11-14 WO PCT/FI1984/000082 patent/WO1985002250A1/en active IP Right Grant
  • 1984-11-14 DE DE8585900108T patent/DE3470095D1/de not_active Expired
  • 1984-11-14 EP EP85900108A patent/EP0163711B1/en not_active Expired

Patent Citations (4)

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