Patent Application
20170144352
The present invention relates to a positioning device, in particular a positioning device capable of controlling a rotary-shaft type turntable of an injection molding machine to be rotated to and positioned at a precise position.
Double color injection molding refers to a plastic injection molding of two or more colors, so that the manufactured products have the effects of two or more colors or materials. When a double color injection molding machine is operated, male and female molds are mounted on a mold plate that can be rotated reciprocally within 180 degrees. After the male and female molds are engaged, a first material feeding step is performed, and then the molds are opened, and the mold plate is rotated by 180 degrees to switch to a male mold position, and the male and female molds are engaged again before performing a second material feeding step, and finally the molds are opened and separate to finish the injection molding process and produce a product. The methods of rotating the conventional mold plate include a rotary-shaft method, a turntable-method, or a combination of the methods applied to the injection molding machine. As to the rotary-shaft method, an output shaft of the speed reducer is rotated by a belt which is looped round the gear of the rotary shaft, so that a mold fixed onto the rotary shaft can be rotated, and an encoder installed to a motor is provided for positioning the turntable. Although this method achieves the positioning effect, yet a backlash occurs easily when the reduction gear installed in the speed reducer is transmitted, and thus resulting in inaccurate positioning.
As disclosed in R.O.C. Pat. No. 498840 entitled “Improved mold turntable positioning structure of an injection molding machine”, two hydraulic shock absorbers are mounted to the top and bottom of the middle of the front wall of the injection molding machine by a positioning seat, and an impact plate is installed at the top of the middle of an outer wall of the turntable, so that the left sidewall of the impact plate abuts an operating end of the hydraulic shock absorber, and the turntable is driven by an hydraulic motor and a power shaft installed at a gear holder at the top of the wall of the injection molding machine to drive a driving gear, a driven gear, and a gear of the turntable to rotate sequentially and linked with the turntable for rotation, the impact plate rotates with the turntable synchronously, and when the right sidewall of the rotating impact plate abuts an operating end at the bottom of the hydraulic shock absorber, the rotating turntable eliminates the high-speed impact by the hydraulic shock absorber, so that the rotating impact plate is stopped and positioned instantly to reduce the time of the mold rotation cycle.
As disclosed in R.O.C. Pat. No. M497087 entitled “Double color injection molding machine with rotary shaft and turntable functions”, the machine comprises a turntable and a rotary shaft installed on the main body, and the turntable has a slot, and the main body has a rotary shaft sleeve, and the rotary shaft sleeve is passed into the turntable slot, and a first bearing corresponsive to the rotary shaft sleeve is installed in the slot and driven by a servomotor, so that when a mold is rotated by a rotary-shaft method, the servomotor drives a driving wheel to link a transmission belt, and the transmission belt drives a driven wheel of the rotary shaft sleeve. As a result, the rotary shaft sleeve and the rotary shaft are rotated simultaneously to achieve the positioning effect.
As disclosed in R.O.C. Pat. No. M476047 entitled “Injection molding machine turntable controlling device”, a servomotor is connected to a turntable mechanism, and a position recorder is provided for outputting position data of the turntable mechanism. After the servo driver receives the position data transmitted from the position recorder, electric power is supplied to drive the servomotor, and the servo driver knows the current position of the turntable mechanism according to the position data outputted by the position recorder to drive the servomotor to control the turntable mechanism to be moved to a target position precisely.
In view of the drawbacks of the conventional method of rotating a rotary-shaft type mold plate that uses a servomotor and a speed reducer to drive the rotary shaft to be rotated and positioned, but the reduction gear of the speed reducer may produce a backlash to cause inaccurate positioning, the inventor of the present invention designed and developed a rotary-shaft type turntable of an injection molding machine in accordance with the present invention.
The present invention adds an encoder installed in the rotary-shaft type turntable positioning device, and uses at least two encoders to lower the error value of gear gap, so as to achieve an inaccurate positioning effect.
To achieve the aforementioned and other objectives, the present invention provides a rotary-shaft type turntable positioning device of an injection molding machine installed at a movable mold base, and the movable mold base includes a rotary shaft sleeve having a driven wheel installed therein, and the positioning device comprises: a rotary shaft, installed in the rotary shaft sleeve, and having a turntable installed at an end of the rotary shaft; a displacement driving mechanism, installed an end of the rotary shaft without the turntable, and provided for driving the rotary shaft to move horizontally; a servomotor, having a first encoder and a driving shaft, wherein the servomotor is capable of rotating the driving shaft according to a received signal, and the first encoder is capable of sending a rotation signal of the driving shaft and transmitting the sensed signal to a central control unit; a speed reducer, installed at the servomotor and having a reduction gear driven by the driving shaft, and the reduction gear having an output shaft, and the output shaft having a second encoder and a driving wheel, and the second encoder being provided for sensing the rotation signal of the output shaft and transmitting the sensed signal to the central control unit; a central control unit, for transmitting a signal to the servomotor and receiving a signal from the first encoder and second encoder according to a default value; and a transmission belt, looped over the driving wheel and the driven wheel, and driven by the servomotor to drive the driving shaft to link the output shaft and drive the driving wheel to rotate the rotary shaft.
Based on the aforementioned structure, the rotary-shaft type turntable positioning device of the present invention uses the displacement driving mechanism to control the rotary shaft installed at the turntable to move forward or retract for the operation of engaging or opening the male and female molds. After the injection molding is completed, the servomotor drives the output shaft of the speed reducer to rotate the driving wheel, and the transmission belt drives the rotary shaft to rotate and position the turntable simultaneously. During rotation, the first encoder installed at the servomotor and the second encoder installed at the speed reducer sense a signal to adjust the speed and position feedback, so that the servomotor can rotate the turntable to a precise position to achieve a quick positioning effect.
The aforementioned and other objectives and advantages of the present invention will become clearer in light of the following detailed description of an illustrative embodiment of this invention described in connection with the drawings. It is intended that the embodiments and drawings disclosed herein are to be considered illustrative rather than restrictive.
With reference to
In
By the first encoder 141 and the second encoder 152 installed at the servomotor 14 and the speed reducer 15 respectively, the signal transmitted from the first encoder 141 and the second encoder 152 to the central control unit 10 may be used to confirm whether or not there is an error occurred when the servomotor 14 drives the driving shaft 142 and the speed reducer 15. After the error is corrected, a command is transmitted to the servomotor 14 to control the rotation of the driving shaft 142, the speed reducer 15 and the driving wheel 153, so as to position the rotary shaft 11 precisely.
