Weighing scales – Weigher responsive material control – Feed
Reexamination Certificate
1999-04-02
2001-10-23
Gibson, Randy W. (Department: 2859)
Weighing scales
Weigher responsive material control
Feed
C177S045000, C177S146000, C073S001130
Reexamination Certificate
active
06307163
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of Invention
The present invention relates to a chemical supplying device. More particularly, the present invention relates to a device that automatically renews a chemical and a method for the same.
2. Description of Related Art
Different chemicals in the industry are often used to achieve different industrial objectives. To accommodate different processes and equipment in a factory, all types of automatic chemical supplying devices have been developed to meet the demands for low cost and high throughput.
Conventionally, in the process for preparing chemicals for use in a process, a chemical of appropriate concentration can be prepared in a mixer tank. The chemical prepared in the mixer tank is conveyed to a buffer tank. The chemical in the buffer tank is then supplied to the required machine by pipes.
To achieve the objective of automatic control, a scale is installed below the mixer tank. The scale measures the net weight of the mixer tank and the chemical therein. When a reading obtained by the scale is equal to the net weight of the mixer tank, it means that the chemical in the mixer tank is used up. Here, the mixer tank is automatically supplied with chemical to ensure that the mixer tank contains enough chemicals to adequately supply the buffer tank.
However, a layer of chemical residue may remain on the wall and bottom of the mixer tank after the mixer tank has been used for a long time. In addition, an exhaust for ventilation affects the weight measurement accuracy of the mixer tank. So, even if the chemical in the mixer tank is used up, the reading measured by the scale is still larger than the net weight of the mixer tank. Thus, the mixer tank is not automatically renewed with the chemical. When the buffer tank needs more of the chemical, a control signal is sent to activate a mixer pump, which conveys the chemical from the mixer tank to the buffer tank. Since there is no chemical left in the mixer tank, the mixer tank pump idles. As a result, the process comes to a standstill.
SUMMARY OF THE INVENTION
The present invention is to provide a chemical mixer tank calibrator and a calibrating method for the same. The calibrator and the calibrating method are appropriate to be used in a chemical supplying device. The chemical supplying device includes a mixer tank, which is used to prepare the chemical. The mixer tank is connected to a buffer tank through a pipe, which has a mixer tank pump thereon. There is a scale below the mixer tank to measure the net weight of the mixer tank and the chemical within. A low level sensor and a high level sensor are mounted respectively at a low level and a high level in the buffer tank. The low level is a point near the bottom of the buffer tank and the high level is a point near the top of the buffer tank. The mixer tank is connected to the chemical mixer tank calibrator. The chemical mixer tank calibrator includes a step motor for supporting the mixer tank, a driver for driving the step motor, and a controller for controlling the driver. The calibrating method of the chemical mixer tank includes setting a reference value Y equal zero. A surface level of a chemical in the buffer tank is checked. When the surface level of the chemical is lower than the low level, the reference is kept reset. In contrast, when the surface level is higher than the low level, a mixer tank pump is activated to draw the chemical from the mixer tank. After the mixer tank pump has been activated for 1 to 5 min, the mixer tank pump is stopped if the surface has reached the high level. Otherwise, buffer tank reaches the high level. However, it will continue with the next step if the liquid in the buffer tank does not reach the high level. The step motor is activated to lift the mixer tank upwards, so that the weight of the mixer tank measured by the scale is reduced and 1 is added to a Y value, which is the number of counts for iterating the activating steps. If X value which is the Y value added with 1 each time the activating step is cycled through is less than 5, the steps of activating the mixer tank pump are repeated, otherwise an initialization step is performed to the step motor followed by triggering the alarm.
Accordingly, the chemical mixer tank calibrator is used in the invention to calibrate the mixer tank and the scale, so that the chemical is automatically supplied to the mixer tank. This prevents the weak point of idling when the mixer tank pump tries to draw the chemical from the mixer tank to the buffer tank when there is no chemical left in the mixer tank.
It is to be understood that both the foregoing general description and the following detailed description are exemplary, and are intended to provide further explanation of the invention as claimed.
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Lai Chien-Hsin
Yu Fu-Yang
Gibson Randy W.
Martine & Penilla LLP
United Microelectronics Corp.
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