Patent GB-1463129-A (GB)
Title: Automatically controlling an installation
IPC: C23D5/00
Filed: 1974-07-04
Abstract: 1463129 Automatic control SOC GENERALE DE FONDERIE 4 July 1974 [27 July 1973] 29795/74 Heading G3N In the automatic programmed control of an installation for the continuous dry enamelling of sanitary articles, e.g. baths, successive values are assigned to each of the operating variable co-ordinates which define the state of the various process activities at any moment during an enamelling cycle and are stored in a digital computer memory. In order to prevent jerky control in the case of those co-ordinates which are required to change comparatively rapidly, e.g. the nine co-ordinates to be controlled at an enamel dusting station, a series of intermediate values between each pair of consecutive values stored are calculated by a law of interpolation to give uniform variation of those co-ordinates. CONTROL APPARATUS, FIG. 5. The enamelling installation is illustrated in Figs. 1-4 (not shown) and includes a loading station, one or more pre-heating furnaces, a station for dusting an article with enamel, one or more glazing furnaces, a cooling component chain, means for conveying the article between the various processing stations, and a digital computer 10. Eighteen co-ordinates are continuously measured by respective transducers and controlled in accordance with programmed data in the computer 10 (Fig. 5) and via a demulti-plexer 20 and respective control chains 101 to 118. Control chains 101-103 are assigned to a rotary conveyer (7) Fig. 1 (not shown) while chains 104-106 are assigned to a rotary conveyer (8). Chains 107-109 control furnaces (2), (3), (5). Chains 110-118 control the nine co-ordinates of the enamel dusting station the latter being the more rapidly changing co-ordinates. Successive values which the eighteen co-ordinates are required to assume during an enamelling cycle are written in tables stored in a peripheral data carrier 60, e.g. magnetic tape. Prior to commencement of a cycle these tables are stored in a central memory in computer 10. A unit 30 is connected to transducers which enable it to display data such as the presence of a bath at the loading station and in a cooling room, and the position of an enamelling table and so on. A unit 40 is a control desk of the computer and displays data such as pre-heating time, time of glazing first and second layers. The demulti-plexer 20 comprises a switching unit (69) Fig. 6 (not shown) connected to transmit  numerical values of each co-ordinate for storage in registers (71). Simultaneously the stored values are transformed by digital/analogue converters (72) into analogue reference voltage for comparison in the control chains with respective voltages from the co-ordinate measuring transducers (e.g. potentiometers) to control various servovalves, motors &c. CONTROL OF DUSTING STATION CO-ORDINATES, FIGS. 7, 9. As shown, a table T is constituted by blocks of data B1-B256, each block containing numerical values at a respective moment in the cycle, of the nine co-ordinates I, R, T &c. to control the enamel dusting process, and a datum indicator In which indicates the time interval #T which must elapse before transfer to the following block. The blocks are spaced over an interval of two minutes, i.e. the duration of the first coat of enamel. Co-ordinate I is the bath inclination, R and T relate to bath movement on a carrier, C represents the azimuth movement of a turret supporting a dusting sieve and so on. In the interpolation of co-ordinate values between those written in table T, each control chain 110-118 is addressed by a number "m" of intermediate co-ordinate values "Y" corresponding to "m" correlative values of time intervals "Z" uniformly spaced within the time interval considered. The values of Y are calculated during movement of the bath &c. to give uniform variation of the co-ordinates as illustrated Fig. 9, which shows fifteen intermediate values between the co-ordinate values written in two consecutive blocks e.g. B 25 , B 26 , the time interval between  each interpolated value being <SP>1</SP>/ 32  secs. The time required for transition between blocks B 25  to B 26  will then be 16 x <SP>1</SP>/ 32  = 0À5 sec during which time the storage registers of the demulti-plexer will have been brought up to date fifteen times with interpolated values and once with the value written in the block B 26 . The number of intermediate values may be selected in dependence upon the requirements of a particular stage in the dusting operation.