Patent GB-439952-A (GB)
Title: Improved controlled withering of tea
IPC: F26B21/08
Filed: 1934-06-12
Abstract: 439,952. Withering tea. MAIN, J. A., Vincent House, Vincent Square, Westminster. June 12, 1934, No. 17422. [Class 34 (ii)] In a method of withering tea in a loft, air is circulated through the loft and its hygrometric state at entry is controlled to maintain as nearly as possible a predetermined ability to take up moisture at a point reached after passing the whole or a predetermined portion of the leaf in the loft, the arrangement being such that, if the air supplied in the moistest of three or more alternative conditions gives a moisture-absorbing capacity below that predetermined at the point in question, a correction is applied causing drier but not substantially warmer air to be admitted, and if after this correction has been applied, the moisture-absorbing capacity is still below that predetermined at the point in question, a correction of a different kind is applied still causing the air admitted to be drier whether or not it is warmer. In the arrangement shown in Fig. 1, a hygrometer 1 is situated at the entrance to a duct 2 through which air issues from a withering loft 3. The duct is formed with a branch 4 divided into two parts 5, 6. A damper 7 is normally maintained in the position shown so that air may issue from the loft through the outlet 5 and fresh air be drawn in through inlet 6 and ducts 10, 9. The duct 10 is provided with a damper 12 normally vertical. The dampers 7, 12 are adapted to be controlled by devices 8, 14, each containing a relay-controlled solenoid which when energized moves the associated damper to a position at right angles to its normal position. When the air in the loft is too dry the hygrometer needle 15 touches a contact 18 thereby completing a circuit to operate the device 8 so that the damper 7 is moved to the position 7<1>. The air in the loft is thus caused to be re-circulated, passing through ducts 2, 10, 9. When the moisture from the leaf raises the humidity of the air the needle 15 leaves contact 18 so that the damper 7 returns to its normal position. If the air in the loft is too humid, the needle 15 engages contacts 16, 17 whereby both dampers 7, 12 are operated so that air issuing from the loft passes through a drying plant 13 before being returned to the loft. In the arrangement shown in Fig. 2, fresh air is used all the time. The hygrometer 1 is situated in the loft where the humidity of the air is likely to be fairly constant, and the direction of circulation of the air through the loft is periodically reversed. Fresh air enters the loft through inlet 20, and may be mixed with dried air by opening a damper 21 associated with a drying plant 13, or with heated air by opening a damper 22 associated with a heater 23. The dampers 21, 22 are controlled respectively by devices 24, 25, which are electrically operated as in the arrangement shown in Fig. 1. When the air in the loft is too dry the hygrometer needle 15 touches contact 26 whereby the device 24 is operated to close damper 21 and prevent admission of dry air. If the air is too humid the needle 15 touches contact 27 whereby the device 25 is operated to open the damper 22 and allow hot air to enter the loft.