Method to meter adhesive for adhesively coating chips, fibers and the like for the manufacture of composite panels, as well as apparatus to carry out the method

Method of metering adhesives being supplied from a supply vessel (1) to a utilization station (35), particularly for coating of chips, fibers and the like with adhesives for processing thereof to make composite panels or the like and having

• a withdrawal pump (30);
• a speed controllable drive motor (44) connected to the supply pump;
• and a control system to control the speed of the motor and hence of the pump, comprising the steps of
• storing the performance characteristics of the withdrawal pump (30);
• (a) providing two measuring or metering cups (5, 6) of predetermined volume;
• (b) providing a supply connection from the supply vessel (1), selectively, to one of the measuring cups;
• (c) filling a first one (5) of the measuring cups with adhesive from the supply vessel;
• (d) withdrawing adhesive from said filled first cup by operation of the withdrawal pump and determining when said first one metering cup has reached a predetermined empty state and providing a "cup empty" signal and sensing the number of revolutions of the withdrawal pump during the actual emptying time;
• (e) filling the second one (6) of the metering cups while emptying the filled first cup (5);
• (f) determining elapsed time between commencement of withdrawal of adhesive by the withdrawal pump and occurrence of the "cup empty" signal to derive an actual measured quantity withdrawal time signal;
• (g) providing a command withdrawal time signal;
• (h) comparing the command withdrawal time signal and the actual withdrawal time signal and deriving a deviation signal by comparing the actual revolutions with the number of command revolutions of the pumps, said command revolutions being based on the stored performance characteristic data of the withdrawal pump;
• (i) controlling the speed of the motor of the withdrawal pump as a function of the deviation signal by
• increasing, upon exceeding the command revolutions, the rotary speed of the withdrawal pump and of a stored number of the command revolutions for subsequent comparison, and decreasing, upon falling below the command revolutions, the rotary speed of the withdrawal pump and decreasing the stored number of command revolutions for subsequent comparison,
• the stored number of command revolutions being incremented or decremented, respectively, by the amount of the difference of the comparison.

Apparatus for metering of adhesives for application thereof to chips, fibers and the like for the manufacture of composite panels having

• a supply vessel for the adhesive (1);
• a withdrawal pump (30) and a suction connection (29) thereto, said withdrawal pump supplying adhesive to a utilization station (35) for coating said chips, fibers and the like;
• two measuring cups (5, 6) having predetermined fill capacity;
• valve means (4) selectively, alternately connecting the supply vessel to one (5) of said cups and the suction line (29) of the withdrawal pump to the other (6) of the cups;
• "cup empty" sensors (15, 16) positioned to sense the fill state of the cups and providing "cup empty" signals;
• a variable speed drive (44) coupled to the withdrawal pump;
• pump revolution scanning means (45) coupled to the pump and providing pump speed signals representative of the revolutions of the pump;
• and variable speed drive control means (33) coupled to the pump revolution sensing means, controlling the speed of operation of said pump, and further coupled to the "cup empty" sensors (15, 16), said control means including
• a computer (51);
• means (42, 47) entering into the computer a command input value representative of a given throughput of adhesive with respect to a given weight or mass of chips or fibers to be coated;
• said computer storing the performance characteristics of the pump and providing pump operating data in the form of binary representation;
• a buffer memory (54) representative of pump throughput for a desired coating;
• a counter (50) receiving the output from said buffer memory and said pump speed signals and comparing said pump speed scanning signals from the pump revolution scanning means (45) with the pump operating data to provide a deviation signal if the throughput of the pump, for emptying of a cup, deviates from a predetermined value as stored in the buffer memory representative of desired coating of the chips or fibers for comparing the commanded throughput of the pump with the time duration between succeeding "cup empty" signals derived from the "cup empty" sensors (15, 16) for control of the variable speed dirve (44) at a speed at which the interval between succeeding "cup empty" signals will be as determined by said command input;
• control connection means (25) between said control means (33) and said valve means (4) to effect change-over of the selective connection of the valve means each time the "cup empty" sensors (15, 16) furnish a "cup empty" signal;
• and
• a correction means (60, 61) connected to receive data representative of said deviation from the counter, the correction means controlling said variable speed drive (44) to change the speed of the pump in a direction to null said deviation,
• said correction means comprising
• a correction memory (60) connected to an electrical control unit (61), said electrical control unit controlling the speed of said variable speed drive, and said correction memory storing data representative of a deviation of pump throughput from desired pump throughput, said correction memory being connected to said computer unit to change the value in the buffer memory (54) representative of desired pump speed for application to the down-counter (50) upon a subsequent emptying cycle of said cups.