Continuous feed tablet coating system

Abstract

A system for coating tablets and other small articles is provided. The system is comprised of an elongate housing containing a drum journalled for rotation about a horizontal axis. The drum has two open ends that receive and discharge a supply of tablets respectively. The drum is rotated about the axis by a drive means to tumble the tablets and advance the tablets through the drum. The system also includes a system for delivering a selected amount of coating to the tablets while they are being tumbled and a feeder for continually feeding tablets at a first end of the housing. The system employs a weir plate for maintaining a depth of tablets within the drum and for controlling the time that the tablets remain in the drum. The system has a tablet discharge region for receiving tablets for discharge.

1 . A system for coating bulk articles comprising:
 a housing comprising opposed first and second ends with an axis extending therebetween;   a pan mounted within the interior of the housing for movement relative to the housing to tumble a bed of said articles within said pan, said pan comprising a first end for receiving said articles and an opposed second end for discharging said articles;   a coating dispenser for dispensing coating onto said articles within said pan;   a weir plate configured to partially obstruct the second end of said pan and maintain a selected spillover height to retain a bed of articles within the pan; and   a mount for mounting the weir plate to the housing to partially obstruct the pan, wherein the weir plate remains static relative to the housing during movement of the pan, said mount permitting selective adjustment of the position of the weir plate to alter the effective spillover height of the weir plate.   
     
     
         2 . The system of  claim 1 , wherein said pan comprises a central axis between said first and second ends and said weir plate mount provides rotational movement of the weir plate about said axis to permit said adjustment of position. 
     
     
         3 . The system of  claim 1 , wherein said pan comprises a rotatable drum having opposed open ends, said weir plate comprising an arcuate lower edge conforming to the interior surface of said drum. 
     
     
         4 . The system of  claim 3 , wherein said weir plate is rotatably mounted to the housing for adjustment about an axis of rotation co-axial with the axis of rotation of said drum. 
     
     
         5 . The system of  claim 4 , wherein said housing comprises opposing first and second end walls at the respective ends thereof, and said weir plate mount comprises a rotatable shaft journalled to the second end wall and a radially-extending link arm connecting the weir plate to the rotatable shaft wherein rotation of the rotatable shaft adjusts the rotational position of the weir plate about an axis of rotation defined by the rotatable shaft. 
     
     
         6 . The system of  claim 5 , wherein said second end wall comprises a port with a door covering said port for accessing the interior of said drum, said shaft being mounted to said door, wherein opening of the door pivots the weir plate outwardly from the housing. 
     
     
         7 . The system of  claim 1  further comprising a feeder for dispensing a stream of bulk articles into a first end of the pan. 
     
     
         8 . The system of  claim 7  further comprising an actuator for adjusting the position of the weir plate and a controller in operative communication with said feeder and said actuator configured to control the average dwell time of tablets within said system by controlling the rate of introduction of said tablets into said system and the spillover height of said weir plate. 
     
     
         9 . A system for coating bulk articles comprising:
 a housing having opposed first and second ends;   a rotatable drum within said housing, said drum having a central axis, a first end for receiving said articles and an opposed second end for discharging said articles;   a coating dispenser for dispensing coating onto a bed of said articles within said pan;   a drive for rotating said drum relative to said housing to tumble said articles within said drum;   a weir plate configured to partially obstruct the second end of said drum and provide a selected spillover height to maintain a selected depth of the bed of articles within the drum; and   a weir plate mount for mounting the weir plate to the housing to partially obstruct the drum, wherein the weir plate remains static relative to the housing during rotation of the drum, said mount permitting adjustment of the rotational position of the weir plate about an axis of rotation co-axial with the central axis of the drum to alter the effective spillover height of the weir plate.   
     
     
         10 . The system of  claim 9  further comprising a feeder for dispensing articles in bulk into said first end of said drum. 
     
     
         11 . The system of  claim 9 , wherein said housing comprises opposing first and second end walls at the respective ends thereof, and said weir plate mount comprises a rotatable shaft journalled to the second end wall, and a radially-extending link arm connecting the weir plate to the rotatable shaft wherein rotation of the shaft adjusts the rotational position of the weir plate about an axis of rotation defined by the rotatable shaft. 
     
     
         12 . The system of  claim 11 , wherein said second end wall comprises a port with a door covering said port located for accessing the interior of said drum, said rotatable shaft being mounted to said door, wherein opening of the door pivots the weir plate outwardly from the housing. 
     
     
         13 . The system of  claim 9  further comprising an actuator for adjusting the position of the weir plate and a controller in operative communication with said feeder and said actuator configured to control the average dwell time of tablets within said system by controlling the rate of introduction of said tablets into said system and the spillover height of said weir plate. 
     
     
         14 . A continuous coating method for bulk articles comprising the steps of providing a system comprising a moveable pan comprising opposed first and second ends, a coating dispenser configured to dispense coating onto a bed of articles within said pan, and a weir plate at the second end of said pan; introducing articles into said first end to form a continuous bed of said articles within said pan; dispensing coating on said articles; providing a selected bed depth within the pan by maintaining a selected spillover height of said weir plate relative to the pan; determining the weight gain of said articles indicative of the amount of coating thereon; and controlling the average dwell time of articles within said pan to obtain a selected coating dispensing exposure time and weight gain of said articles by controlling the spillover height of the weir plate relative to the pan, wherein said weir plate remains static relative to the housing as the pan is moved. 
     
     
         15 . The method of  claim 14 , wherein said pan comprises a rotatable drum, said method comprising the steps of tumbling said articles within said drum by rotation of the drum, and controlling the spillover height of said weir plate by selectively adjusting the rotational position of the weir about the elongate axis of the drum. 
     
     
         16 . The method of  claim 14  comprising the step of further controlling the rate of transit of said articles through the drum by controlling the rate of introducing articles into said drum. 
     
     
         17 . The method of  claim 14 , wherein said system is configured to dispense said coating in either of a selected batch or continuous coating mode, said method comprising the step of coating an initial charge of articles in a batch mode, and subsequently transitioning to a continuous coating mode by introducing a continuous stream of articles into said pan, and adjusting the position of the weir to permit continuous throughflow of said articles through the pan.