Between the rear platen 2 and the movable platen 3 a toggle mechanism 6 is disposed. A ball nut provided on a crosshead 6a of the toggle mechanism 6 engages a ball screw 7 mounted on the rear platen 2 so as to be rotatable but unmovable in an axial direction. A belt 9 is suspended between a pulley 10 provided on the ball screw 7 and a pulley 11 provided on an output shaft of a clamping servomotor 8 used for clamping. The ball screw 7 is driven by the drive of the clamping servomotor 8 via the pulley 11, the belt 9, and the pulley 10, causing the crosshead 6a of the toggle mechanism 6 to advance and retreat (that is, to move laterally left and right in
It should be noted that reference numeral 16 designates an eject mechanism provided on the movable platen 3 for pushing a molded product out of the interior of the mold, which works by driving an eject motor 16a during opening of the mold so as to push an eject pin into the interior of the mold, thus pushing the molded product out of the mold. In addition, reference numeral 17 designates a clamping force adjustment mechanism provided on the rear platen 2, which drives a clamping force adjustment motor 17a that rotates nuts that engage screws mounted on the tie bars 4 through a transmission mechanism so as to change the position of the rear platen 2 with respect to the tie bars 4 and thereby adjust the clamping force. The eject mechanism 16 and the clamping force adjustment mechanism 17 are not directly related to the present invention and detailed descriptions thereof are therefore omitted.
Reference numeral 15 designates a controller for controlling the injection molding machine, and as conventionally comprises a processor, memory units such as a ROM, a RAM, etc., an input/output interface, and a motor control circuit that controls the position and speed of the servomotors that drive the movable parts of the injection molding machine. The controller 15 controls the driving of the movable parts of the injection molding machine such as the clamping servomotor 8, the eject motor 16a, and the clamping force adjustment motor 17a described above. Further, the position/speed detector 12 mounted on the clamping servomotor 8 is connected to the controller 15 so that signals from the position/speed detector 12 are fed back to the controller 15.
The construction described above is the same construction as that of the conventional toggle-type clamping device, and does not differ from the related art. The distinctive feature of the present invention is the addition of a detection unit to the toggle mechanism 6 side of this type of toggle-type clamping device that detects the arrival of the crosshead 6a of the toggle mechanism 6 at a predetermined position. Specifically, in the present embodiment, as the detection unit, a dog 13 is provided on the crosshead 6a and a proximity switch 14 that detects the dog 13 when the dog 13 reaches a predetermined position is provided on the rear platen 2. The proximity switch 14 is also connected to the controller 15.
When an opening or closing movement of the mold begins (Step S1), the processor of the controller 15 determines whether or not the crosshead 6a has reached the set predetermined position based on the position feedback signals from the position/speed detector 12 mounted on the clamping servomotor 8 (Step S2). When the processor determines that the crosshead 6a has reached the predetermined position based on the position feedback signals, it then determines whether or not a signal indicating sensing of the dog 13 has been inputted from the proximity switch 14 (Step S3). If no abnormality such as breakage of the belt 9 has occurred, the proximity switch 14 senses the dog 13 when the position of the crosshead 6a determined based on the detection by the position/speed detector 12 has reached the predetermined position, and therefore the opening or closing movement of the mold continues as is.
By contrast, when it is determined that the proximity switch 14 has not sensed the dog 13 in Step S3, the processor outputs an alarm and stops the movement of the mold (Step S4).
Thus, as described above, simply by adding a simple mechanism comprised of the proximity switch 14 and the dog 13 to the conventional toggle-type clamping device, abnormalities such as a break in the belt 9 and the like can be detected simply, inexpensively and securely by utilizing the position/speed detector 12 or the like mounted on the clamping servomotor 8 of the conventional toggle-type clamping device.
It should be noted that although in the above-described embodiment the sensing unit that senses the arrival of the crosshead 6a at the predetermined position is comprised of the dog 13 and the proximity switch 14, another equally simple sensing unit such as a limit switch may be used instead.
Number | Date | Country | Kind |
---|---|---|---|
231705/2006 | Aug 2006 | JP | national |