Patent Application
20050098911
Not Applicable
Not Applicable
Not Applicable
1. Field of Invention
This invention relates to a system and method for protecting injection molds.
2. Prior Art
Articles molded in an injection mold may not eject from the mold's ejection sequences. The inherent characteristics of the material being molded, the geometry of the article, or molding imperfections, such as flash, often cause an unsuccessful ejection. Portions of molded articles may remain in the mold after the ejection sequences due to a failure in the ejection system, breakage of the molded article, or insufficient material being supplied to the mold cavity. If the molded articles, or portions thereof, are not properly ejected from the mold prior to the mold closing, mold damage can occur or subsequent molded articles may be defective. Molding machines are often equipped with a low-pressure mold protection feature, closing the mold at a lower pressure in an attempt to detect any resistance at mold closing due to an unwanted article in the mold. Low-pressure mold protection does not protect the mold when the low pressure is enough to damage the mold, or when improper ejection occurs often.
Article-sensing vision systems and radiation emitting and receiving article sensors are currently utilized to protect injection molds. Radiation emitting and receiving article sensors are often utilized to function as drop sensors or article detection sensors. Drop sensors are utilized to verify that a molded part fell, or dropped, past the sensor, providing a high degree of confidence that the molded part cleared the mold. Article-detection sensors detect the absence or presence of an article in the mold. Molds equipped with mold protection sensors vary in the amount of monitored zones and the functions the zones perform. These zones may be performing drop monitoring or article detection within the mold. Article-detection controllers require operator intervention to set the amount of monitored zones and define the function of each zone. This requirement for operator intervention is undesirable since an incorrect setup can lead to improper protection of the mold. This risk can be mitigated through the purchase of multiple article-detection controllers, dedicating each controller to a specific mold, or group of molds, with a predetermined amount of utilized zones with each zone being predetermined whether it is performing drop monitoring or article sensing.
Protecting the mold, eliminating the need for dedicated controllers, simplifying mold installations, and reducing the risk of improper mold protection are important since prevention of mold damage directly relates to the cost of the molded articles and the competitiveness of the molder.
Accordingly, several objects and advantages of my invention are:
Further objects and advantages of my invention will become apparent from a consideration of the drawings and ensuing description.
This invention provides a system and method of protecting a mold.
Operation—
Article-detection devices, such as radiation emitting and receiving article sensors 14, 16, 18, 20, are strategically placed in the mold to detect a molded article, or portion thereof 30 at known positions. Placing sensors that inspect below the molding position enable the sensors to perform drop monitoring 14, detecting the molded article, or portion thereof 30, as it falls from the mold. Sensors that inspect the molding position enable the sensors to perform article detection 16, 18, 20, detecting the molded article, or portion thereof 30, that is in the mold.
The article-detection controller 24 monitors the condition of all zones and permits or prohibits the molding machine controller 26 from closing the mold and initiating the next molding cycle. The mold ejector system 22 is utilized to eject the part from the ejector-half of the injection mold 10, and can encompass all methods of ejection known to the ordinarily skilled artisan such as, and not limited to, mechanical ejection and pneumatic ejection. If all drop monitoring sensors 14 have been satisfied, and the molded article, or portion thereof 30, is not detected by the article-detection devices 16, 18, 20, the mold is allowed to close and start its next cycle. If all drop monitoring sensors 14 have not been satisfied, or the molded article, or portion thereof 30, is detected by the article-detection devices 16, 18, 20, the mold is not allowed to close and start its next cycle.
Operation—
Prior to part ejection, the molded article, or portion thereof 30, will be located in the molding area and all monitoring zones will be unsatisfied. The conditions of zones prior to part ejection are recorded 44 since any unsatisfied zone is being utilized for part monitoring. Any unutilized zones are jumped and are permanently satisfied, and therefore are satisfied prior to part ejection. The mold is prevented from closing 48 and initiating the next cycle. After all unsatisfied zones have become at least temporarily satisfied 50, the condition of zones after ejection are recorded 52. An article-detecting zone will remain satisfied after part ejection, while drop-monitoring zones will only be momentarily satisfied. The mold will then be allowed to close 56. During the master cycle, the record of zone conditions prior to part ejection 44 are recorded as a master record of zone conditions prior to ejection 46. During this master cycle, the record of zone conditions after ejection 52 are recorded as the master record of zone conditions after ejection 54. The master cycle does not necessarily have to be the first cycle, but can be any prior cycle to the current cycle. When the master cycle is defined by the article-detection controller, only passive operator supervision is required to ensure that the mold and mold protection system performed satisfactorily during this master cycle. Any subsequent cycles to the master cycle then record the current record of zone conditions prior to ejection 58 and the current record of zone conditions after ejection 60, enabling a comparison with the master records 46, 54. The current and master records of zone conditions after ejection are compared 62, and if they match, the current and master records for zone conditions prior to ejection are compared 64. If all unsatisfied zones have become at least temporarily satisfied, and both comparisons match, the mold is allowed to close 56, starting the next molding cycle.
From the description above, a number of advantages of the system become evident:
These advantages enable a lower risk and reduction of capital than with existing mold protection methods.
Although the description above contains many specifics, these should not be construed as limiting the scope of the invention, but as merely providing illustrations of some of the presently preferred embodiments of this invention. For example, the article-detection controller and molding-machine controller can be one and the same, wireless communications can be utilized to communicate between the devices, the master cycle need not be the first cycle, etc. The scope of the invention should be determined by the appended claims and their legal equivalents, rather than by the examples given.
