Plastic article or earthenware shaping or treating: apparatus – Control means responsive to or actuated by means sensing or... – Control means responsive to product weight or dimension
Reexamination Certificate
1999-06-16
2001-12-04
Nguyen, Nam (Department: 1722)
Plastic article or earthenware shaping or treating: apparatus
Control means responsive to or actuated by means sensing or...
Control means responsive to product weight or dimension
C425S141000, C425S145000, C425S149000, C425S150000, C425S345000
Reexamination Certificate
active
06325609
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to a compression molding machine for powder material which compresses powder material so as to mold a medical tablet or something like that.
BACKGROUND OF THE INVENTION
Generally it is difficult for a molding machine which produces a plurality of products successively in a short time to measure an amount of powder material before the powder material is molded into a product in spite the products such as tablets are required to have a uniform weight. For a molding machine having an arrangement in which a punch is inserted into a die by a predetermined depth to compress powder material into a product a ratio of the weight of the product to the compressive pressure applied to the product is approximately one to one. In view of the above, compressive pressure acting on the powder material is detected and the amount of the powder material to be filled into the die is automatically controlled so that the detected compressive pressure becomes identical to a reference value of pressure which has previously been calculated in correspond with a target amount of the powder material. In accordance with a method which controls weight of a product indirectly, however, the weight of the product might fluctuate because a punch or a die expands or shrinks due to heat or a flow of the powder material fluctuates even if the compressive pressure is controlled to be identical to the reference value of pressure. Then conventionally the amount of the powder material to be filled into the die is adjusted so that the weight of the product which has been periodically sampled becomes identical to a reference value of weight and a reference value of pressure is calibrated based on compressive pressure measured after the amount of the powder material is adjusted.
Recent demand requires that thickness of products be within a certain range in order to make a process of packing the products smooth. In this case, position of a punch is controlled to make the thickness of a product identical to a reference value of thickness and the reference value of pressure is calibrated based on the compressive pressure when the thickness of the product is within the range.
However, weight and thickness are interconnected. Then if either one of them is controlled, the other would also be affected. As a result, it has conventionally been considered to be difficult to control both weight and thickness together and both of the weight and thickness can not automatically be controlled at once. Therefore, a skilled person adjusts the weight and thickness together manually, which prevents the manufacturing process from being automated. This is one of the factors which prevents productivity from being improved.
SUMMARY OF THE INVENTION
In order to solve the above-mentioned problems, the invention is intended to automate a process of compression molding fully and to provide high quality products constantly by the following process. Weight and thickness of sampled products are measured and both of the weight and thickness of the products are feedback-controlled together by comparing the measured values of weight and thickness with predetermined reference values of weight and thickness respectively.
The compression molding machine for powder material in accordance with the invention comprises, as shown in
FIG. 1
, a compressing means AA which compresses powder material filled between compressing components so as to mold the powder material into a product by making the compressing components approach each other to a predetermined distance, an amount adjusting means BB which adjusts an amount of the powder material to be filled, a pressure detecting means CC which detects compressive pressure applied to the powder material by the compressing means BB, and a basic control means DD which controls the amount adjusting means BB so that the compressive pressure detected by the pressure detecting means CC becomes approximate to a reference value of compressive pressure which has previously been calculated in accordance with the predetermined reference amount of the powder material, and is characterized by that provided with a measuring means EE which samples the product automatically and measures weight and thickness of the sampled product, a position adjusting means FF which adjusts a predetermined distance between the compressing components, a weight control means GG which is used alternatively to the basic control means DD and controls the amount adjusting means BB so that the weight of the product measured by the measuring means EE becomes approximate to a predetermined reference value of weight, a thickness control means HH which is used alternatively to the basic control means DD and controls the position adjusting means FF so that the thickness of the product measured by the measuring means EE becomes approximate to a predetermined reference value of thickness and a reference pressure calibration means II which calibrates the reference value of pressure based on the pressure measured at a time when both of the measured weight and thickness of the product are within the limits of tolerance set in accordance with the reference value of weight and thickness. The alphabet JJ in
FIG. 1
shows a switching element which switches the basic control means DD and the weight control means GG or the thickness control means HH alternatively and the alphabet SK is a signal to switch the switching element JJ.
In accordance with the arrangement, since the product is automatically sampled and feedback-controlled in weight and thickness and the reference value of pressure is calibrated while controlled by the basic control means DD, it is possible to automatically produce high quality products constantly uniform in weight and thickness although the compressing component might expand due to high temperature or flow of powder material might fluctuate. As a result, productivity can be improved and the cost can be decreased because of full-automation.
In order to simplify and stabilize control it is preferable to have an arrangement in which the thickness of the product is controlled by the thickness control means HH after the measured weight of the product is controlled to be within the limits of tolerance of the reference value of weight by the weight control means GG.
Measurement of weight may preferably be represented by that a plurality of products are sampled and average weight and thickness of the sampled products are calculated by the measuring means EE and that the average weight and thickness are utilized as the measured weight and thickness respectively.
In order to carry out automatic operation preferably it is preferable that the products are sampled at predetermined intervals.
In order to stabilize weight control by the weight control means GG it is preferable that a method for controlling the weight control means can be varied in a plurality of steps based on an amount of deviation of the measured weight of the product from the reference value of weight. In order to stabilize thickness control by the thickness control means HH it is preferable that a method for controlling the thickness control means can be varied in a plurality of steps based on an amount of deviation of the measured thickness of the product from the reference value of thickness.
In order to avoid unnecessary calibration of the reference value of pressure and to stabilize control by the basic control means DD it is preferable that a dead zone is provided with the reference value of pressure being a center of the dead zone and that no calibration is conducted to the reference value of pressure by the reference pressure calibration means II if an amount of deviation of the measured pressure from the reference value of pressure is within the dead zone. In this case it is preferable that a plurality of ranges of the dead zone can be set.
In order to meet user's requirements or to deal with various kinds of powder material it is preferable that a method for calibrating the reference value of pressure by the reference pressure
Banner & Witcoff , Ltd.
Heckenberg Donald
Kikusui Seisakusyo Ltd.
Nguyen Nam
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