Research On Tire Mold Structure

According to the structure of the tire mold, it is divided into a tire half mold and an active mold. The structure of the tire half mold is relatively simple, mainly including upper and lower side plates and upper and lower steel rims. The parting surface of the upper and lower side plates is on the center line of the tire pattern. The upper and lower molds are opened when the mold is working. The structure of the active mold is relatively complex, mainly divided into two parts: the cavity plate and the mold shell. The cavity plate is a part that directly contacts the tire blank, mainly including the pattern block, upper and lower side plates, and upper and lower steel rims; the mold shell is the guide mechanism of the mold, which is used to control the opening and closing movement of the mold. It mainly includes the middle mold sleeve, bow seat, upper cover, base, wear-resistant plate, guide strip, mounting ring, lifting block, etc. When the mold moves, the bow seat and the pattern block perform radial opening and closing movements.
The guide surface of the active mold guide mechanism is an inclined plane, which is called an inclined plane type tire active mold. During the opening and closing process of the inclined plane type mold, the middle mold sleeve and the bow seat are in plane contact. The number of mold bow seats is generally 8 to 10, and 8 to 10 inclined planes need to be processed on the bow seat and the matching middle mold sleeve. In order to ensure that the finished tire does not have rubber edges and misaligned appearance quality problems, the mold clamping accuracy of the inclined plane mold is very high. The inclined plane processing on the mold requires 8 to 10 planes to be equally divided into a circle and the planes are all centripetal, and the centripetal angle of the inclined plane should be consistent. Ordinary processing machine tools cannot meet such high precision requirements, and special CNC machine tools are required for processing. After the mold parts are worn, the diameter error will appear inside the pattern block, which will reduce the roundness of the vulcanized tire and easily cause tire rubber edge problems. However, the inclined plane mold has low requirements for the flatness of the upper and lower hot plates of the vulcanizer and has good adaptability. The guide surface of the active mold guide mechanism is a conical surface, which is called a conical surface active mold. Compared with the inclined plane, the conical surface has good machinability, and ordinary machine tools can meet the precision requirements. The assembly precision requirements of the conical mold are relatively low. After the mold parts are worn, the circumferential deviation can be automatically compensated, which has little effect on the roundness of the vulcanized tire, and has no obvious effect on the rubber edge and misalignment of the tire. However, during the opening and closing of the mold, the wear-resistant plates on the bow seat and the middle mold sleeve gradually transition from line contact to conical surface contact, resulting in uneven wear of the wear-resistant plates, unstable mold movement, and low adaptability to the vulcanizer.
At present, there are two heating methods in the tire vulcanization process: steamer type and hot plate type. Steamer type heating is to heat the mold in a sealed vulcanizing tank; hot plate type heating is that there are two heating sources on the mold: one is the upper and lower hot plates of the vulcanizer, with a temperature of about 150°C, which is used to vulcanize the tire sidewall; the other is that the air chamber of the middle mold sleeve of the mold is passed with water vapor of about 160°C, and the heat energy is transferred inward through the bow seat to the pattern block to vulcanize the tread pattern part. The difference between the steamer-type and hot plate-type mold structures is that the steamer-type middle mold sleeve does not have an air chamber, while the hot plate-type middle mold sleeve has an air chamber that is filled with superheated steam as a heat source for the mold. The mold needs to be preheated for a period of time before the tire is loaded into the vulcanizer so that the mold reaches the temperature required for tire vulcanization. The vulcanizer drives the mounting ring and the middle mold sleeve to move upward, while the bow seat drives the tread block to move radially to open the mold. The robot then grabs the tire and places it on the vulcanizing bladder of the center mechanism of the vulcanizer. After positioning is completed, the upper cover and upper side plate of the mold move downward under the action of the vulcanizer, and the bow seat and the tread block are radially molded into a full circle under the force applied by the middle mold sleeve. The tire is heated for a period of time at a certain temperature and pressure, and the tire is vulcanized into a finished tire.