The domestic QZ folio cutter is a kind of packaging and printing equipment produced in China in the 1980s. Because of its simple structure, low energy consumption, long life and low price, the production and sales have been very good, and there are still tens of thousands of users. However, because the device usually uses a mechanical tension spring as the paper pressing mechanism, and the electromagnetic clutch structure as the cutting knife transmission mechanism, it is easy to cause a continuous knife and lead to safety accidents.
For this reason, this paper carefully analyzes the original paper cutter design, finds out the inadequacies in the original design, and proposes a safe and reliable paper cutter new technology transformation plan.
Analysis of the reason of paper cutter with knife
After pressing the "Cut" button, the cutter will run up and down more than twice to be called a continuous cutter. In view of the structural characteristics of the QZ202 folio cutter, the main causes of the continuous knife are the failure of the cutting knife limit switch or failure to hit the upper limit switch, and the relay contacts are stuck or sluggish.
Solution to the cutter of the paper cutter
1. The top of the cam of the limit switch of QZ202 folio cutter has a tapered structure. The tapered structure makes the cutter body of this type of paper cutter fall faster. When the blade holder body is at the lowest position, it is also the instantaneous cutting point with the largest cutting force. The tip of the cone body hits the limit switch, and the blade holder body can quickly return. The stop-and-stop switch structure has a short power-off time (the position of the top of the cone), and instantaneous interruption and instantaneous conduction are a major hidden danger to the continuous knife.
In this regard, referring to the structure of the German POLAR paper cutter's stop-and-stop limit switch structure, the top of the cutter's limit switch cam is changed from a cone-shaped impact block to an oval-shaped stop-and-stop switch mechanism, which lengthens the power-off buffer at the top position It can effectively prevent the occurrence of the continuous knife event caused by the transient interruption. Shanghai Tobacco Packaging and Printing Co., Ltd.
2. If the limit travel switch is out of control, the limit switch will not be broken. QZ202 has two sets of contacts for the limit switch on the cutter, but only one of them is used. During the work of the cutter, the contacts will inevitably fail occasionally, that is, when the limit stroke switch is hit, Unable to power off on time. The use of a free set of contacts in the travel switch increases the probability of power failure, and reduces the probability of continuous tooling caused by contact failure without increasing costs by more than 50%.
3. Cutting control relay. The intermediate relay selected for the QZ202 folio cutter is the JZ7-44 type, which is only suitable for non-frequent action occasions. The contacts can circulate a resistive load AC380V / 5A, DC127V / 5A. However, the secondary output load of this type of paper cutter is DC32V / 3.2A, and it is an inductive load. The impact current is large, which is more than 7 times higher than the contact withstand voltage. Therefore, the contact spark is large, easy to burn, blacken, etc., increase the contact resistance and reduce the loop voltage. What is more serious is that the contacts frequently carry the impact of large inductive currents for a long time, which causes the cold welding of the contacts to stick or slow the movement, and the power failure is slow, resulting in the failure of the continuous knife. In actual production, because the overcurrent of the JZ7-44 contact is too small, the failure is fast, which causes some users to replace the relay after running the new machine for several months.
CJ10-20A with arc-extinguishing cover contactor has the characteristics of large contact overcurrent, small spark, long life and sensitive action, which is suitable for frequent opening and closing. Practice has proved that this model uses CJ10-20A with arc extinguishing cover contactor, the effect is remarkable, and it can greatly reduce or eliminate the event of continuous knife.
4. Brake device. In order to save money, many manufacturers use the principle of circuit braking, that is, the way of cutting off the power supply of the cutter motor through the upper and lower limit sensors, and the QZ202 is no exception to the paper cutter. Such a device may cause extremely dangerous situations such as a continuous knife caused by a sliding knife in the event of a sudden power failure or a loose socket. In order to prevent this from happening, it is necessary to use a motor assembly with a mechanical brake device, so that no matter what circuit failure occurs, the motor is locked to avoid accidents.
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