Patent EA-000268-B1 (EA)
Title: Apparatus for drying of timber
Inventor: GERRISH PHILIP
IPC: F26B25/22
Filed: 1996-09-12
Abstract: 1 Timber drying apparatus comprising a housing for containing a quantity of timber, temperature sensing means arranged to sense the temperature of timber within the housing, means for heating timber contained within the housing and control means for varying the means for heating the timber in response to the sensed temperature characterised in that the housing comprises or includes a cavity (4), the means for heating is a microwave generator (1) coupled to the cavity (4) by at least two ducts (2) for introducing microwave energy into the cavity (4) and weight sensing means (8) for sensing the weight of timber within the cavity (4). 2 Apparatus as claimed in Claim 1 characterised by a ventilation means (10, 11) arranged to displace air through the cavity (4) to regulate humidity and/or air temperature within the cavity (4). 3 Apparatus as claimed in Claim 2 characterised in that the ventilation means (10, 11) includes a humidity sensor (9, 12) at an air inlet (10) to or an air outlet (11) from the cavity, the humidity sensor (9, 12) being adapted to provide a signal output representing the humidity of air in the vicinity of the sensor; the signal output being used as a input to regulate operation of the ventilation means (10, 11). 4 Apparatus according to any preceding Claim characterised by a timber carriage (16) arranged to support timber within the cavity (4). 5 Apparatus according to Claim 4 characterised by means (7) for the carriage (16) whereby an oscillatory or rotatory motion can be imparted to timber supported by the carriage (16) within the cavity (4). 6 Apparatus as claimed in any preceding Claim characterised by stirring means (3) within the cavity (4) operable to vary spacial distribution of microwave energy within the cavity (4). 7 Apparatus as claimed in any preceding Claim characterized by aperture and a closure (5) therefore, the closure being operable to provide access to the interior of the cavity (4) by way of the aperture whereby timber can be inserted into or removed from the cavity. 8 Apparatus as claimed in Claim 7 characterised by a plurality of apertures and closures (5) therefor means regulating the opening or closing of the closure of each aperture on a continuous basis to periodically provide for the introduction of timber into the cavity and/or the extraction of timber from the cavity by way of one or more of the apertures. 9 Apparatus as claimed in any preceding Claim characterized by temperature sensing means (13) including at least one inflared pyrometer arranged for measuring the surface temperature of wood within the cavity. 10. Apparatus as claimed in any preceding Claim characterised in that the temperature sensing means (13) includes at least one fibre optic temperature sensor. 11 Apparatus as claimed in any preceding Claim characterised by the control means being operable to derive a measure of the rate of change of weight of timber located within the cavity from the sensed weight in order to derive a measurement of the race of drying of the timber. 12 Apparatus as claimed in Claim 11 characterised in that the control means are arranged to control the power output of the microwave source (1) to ensure that the drying rate of wood within the cavity (4) is kept below a predetermined maximum. 13 Apparatus as claimed in Claim 11 or Claim 12 characterised in that the control means serve to indicate that wood within the cavity (4) is sufficiently dry such as when; the drying rate of the wood over a predetermined time is zero or less than a predetermined maximum; or the total weight loss during drying is the same or more than a predetermined minimum weight loss. 14 Apparatus as claimed in any preceding Claim characterised in that the microwave generator (1) is operable to produce several different continuous or intermittent power outputs. 15 A method of drying timber within a housing containing a quantity of timber and temperature sensing means arranged to sense the temperature ol' timber within the housing and means for heating timber contained within the housing along with control means for varying the means for heating the timber in response to the sensed temperature characterised by the steps causing the housing to serve as microwave cavity (4), using a microwave generator to inject microwave energy the cavity (4) and so into timber located therein, repeatedly sensing the weight and/or temperature of timber within the cavity (4) and controlling power injected into the cavity (4) by the generator (1) in response lo sensed weight and/or temperature of timber in the cavity (4).