Production process of PVC ball valve
Production process of PVC ball valve is characterized by the following steps: A. making the integral valve core which fixedly connects the stem and the ball; B. putting the ball of the integral valve core and the stem part connected with the valve ball into the mould for making the plastic ball valve body; C. heating and melting the plastic material; The plastic ball valve body is formed by cooling in the die. Each side of the plastic ball valve body has an opening to the position where the valve ball is located. The top of the valve body has a stem extension outlet. After the plastic ball valve body is cooled and formed, the ball of the one-piece valve core and the connecting part of the valve stem are completely confined to the plastic ball valve body. The stem end of the integral spool extends outward from the stem outlet located at the top of the plastic ball valve body, while the ball of the integral spool contacts or has a clearance between the body cavity of the plastic ball valve body and the body cavity of the plastic ball valve body. One of the openings on both sides is connected with a plastic valve cover with a through hole, and the through hole of the plastic valve cover is connected with the flow passage in the plastic valve body.
In step a, One-piece spools can be made from a variety of materials. For example, when the strength of an integral valve core is required to reach a high standard, the integral valve core can be made of metal material; when the integral valve core is required to be light, corrosion-resistant and simple to process, the integral valve core can be made of plastic material; when the strength of the integral valve core is high and corrosion-resistant, the integral valve core can be made of plastic material; and when the integral valve core is required to be corrosion-resistant, the integral valve core can be made of plastic material. The body valve spool can also be made of composite materials. Here, the composite material refers to the material which is composed of at least two or more kinds of materials, such as the composite material made of plastic wrapping metal, or the composite material made of different plastic materials layered wrapping and so on. At the same time, the valve stem and ball can also be made of other materials such as ceramics. Of course, two different materials can also be used to make the stem and ball respectively. For example, the metal-plastic composite valve core can be made from the metal skeleton and the plastic coating coated with the metal skeleton.
In step b, in order to set the sealing structure between the valve stem and the valve body in the follow-up processing of the ball valve, the filling box insert on the stem of the integral valve core can also be placed in the mould for making the plastic ball valve body, so that the placement position of the filling box insert and the filling box of the formed plastic ball valve body can be obtained. It fits in the position. The filler box insert can not only connect with the plastic ball of the integrated plastic valve core in the inner space of the plastic valve body, but also allow the filler box insert to be partially embedded on the plastic valve body, not intersect with the plastic ball of the integrated plastic valve core in the inner space of the plastic valve body, and can also allow the filler box insert to be fully embedded. Fixed on the plastic valve body, but still not intersected with the plastic ball of the integrated plastic valve core in the internal space of the plastic valve body.
In step c, the process of forming the plastic ball valve body by heating and melting the plastic material and cooling in the mould can be conveniently completed by injection moulding on the injection moulding machine (of course, other thermoplastic moulding methods are not excluded). Because injection moulding can improve the speed and accuracy of production, ensure the qualified rate of products, suitable for large-scale industrial production, so I particularly recommend this moulding method.
In addition, in step c, I recommend the use of polyethylene material to make plastic ball valve body, but the material for making plastic valve body is not limited to polyethylene material only. For example, a variety of plastic materials, such as polypropylene, polyvinyl chloride, ABS and so on, can be used to manufacture plastic ball valve body. At the same time, the plastic ball valve body can also be a plastic ball valve body with a framework composed of metal or other materials.
In step d, the fixed connection between the plastic valve cover and the plastic ball valve body can adopt a variety of fixed connection modes, including various bonding (hot melt bonding or ultrasonic bonding, adhesive bonding, etc.) and threaded connection modes. From the point of view of ease of manufacture, I recommend bonding to connect the opening of the plastic ball valve body to the plastic valve cover.
The bonding between plastic valve cover and plastic valve body mentioned in this paper includes two situations: A. direct bonding between plastic valve cover and plastic valve body (adhesive bonding or hot melt bonding or ultrasonic bonding); B. indirect bonding between plastic valve cover and plastic valve body (adhesive bonding or hot melt bonding or ultrasonic bonding) through joints.
When direct bonding is used between the plastic cover and the plastic body, the two can be made to be end-to-end or socket bonding. When the two are end-to-end bonding, the plastic cover and the plastic valve body shall be respectively provided with a matching bonding end-to-end, and then the plastic cover and the plastic valve body shall be bonded with the above-mentioned bonding end-to-end. Of course, one part of the plastic valve cover can be bonded with the plastic valve body, the other part can be connected with the plastic valve body by threads and other ways. From the point of view of easy manufacture, I particularly recommend that the bonding between the plastic valve cover and the plastic valve body be hot-melt socket bonding.
In addition, in the case of partial contact between the ball of the integral spool and the inner cavity of the valve body of the plastic ball valve and forming a sealing pair, the sealing surface can be no longer set on the plastic valve cover, that is to say, a one-sided seal can be formed. Of course, the sealing surface can still be set on the plastic valve cover, that is, a double-sided seal. In the case of complete separation between the valve ball of the spool and the inner chamber of the plastic ball valve body or partial contact without forming a sealing pair, the sealing surface of the sealing pair must be set on the plastic valve cover to match the ball surface of the integral spool, thus forming a one-sided seal.
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