Plastic article or earthenware shaping or treating: apparatus – Control means responsive to or actuated by means sensing or... – Means responsive to abnormal condition completely stop...
Reexamination Certificate
1998-10-02
2001-01-09
Heitbrink, Tim (Department: 1722)
Plastic article or earthenware shaping or treating: apparatus
Control means responsive to or actuated by means sensing or...
Means responsive to abnormal condition completely stop...
C425S150000, C425S169000, C264S040500, C100S046000, C100S099000, C100S25800A
Reexamination Certificate
active
06171092
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an apparatus and method for maintaining proper alignment between platens of a mold clamp for a molding machine and, more particularly, to the use of electromagnetic sensors to detect misalignment of the platens at all stages of the molding process.
2. Description of the Related Art
Very large molding machines use platens which, if misaligned when moving, can cause substantial mechanical damage to the machine or the mold installed in it. The problem of maintaining platen parallelism or “leveling” during clamping operations for processes like stamping metals, compression molding, or injection molding is well-known.
U.S. Pat. No. 3,640,660 issued to De Mets (incorporated herein by reference) discloses a vertical press with a means for measuring the relative distance between its two pressure platens when the platens are in a closed operative position. U.S. Pat. No. 5,196,150 issued to Mimura, et al. (incorporated herein by reference) discloses another vertical press in which the stroke deviation for the compression can be adjusted by detecting the position of the moving platen during the compression stroke so that levelness of the moving die can be maintained during the compression stroke. U.S. Pat. No. 5,314,327 issued to Stein and U.S. Pat. No. 5,454,709 issued to Leonhartsberger, et al. (both incorporated herein by reference) disclose a horizontal clamp with a moving platen having adjustable means for maintaining parallelism between the platens. These means are mechanical and need to be manually adjusted. Neither of these patents discloses means for sensing lack of parallelism automatically.
None of the above-referenced patents teach how misalignment of platens can be detected at any point over the entire operating stroke of the moving platen. The prior art teaches how misalignment can be detected and corrected only after the moving platen has closed and is being subjected to molding pressure, which subsequently causes the misalignment.
Causes of misalignment other than molding pressure, however, can cause the moving platen to become misaligned prior to the time the platens are closed. For example, a molded part may not eject properly from the mold and thus become trapped between the two mold halves as the moving platen closes the mold. If this entrapment is on one side of the mold only, a significant out of balance force will be applied to the moving platen causing it to cock or become seriously misaligned while still moving.
Another cause of misalignment could be the malfunction of a robot or part removal system in such a way that the robot or part of its tooling does not clear out of the path of the moving platen or the mold attached thereto. Collision between the robot or part of its tooling and the moving platen or mold could cause a misalignment that would go undetected in prior art devices.
Accordingly, there is a need in the art for a way to detect misalignment during the operating stroke of the moving platen, and promptly correcting such misalignment as soon as it is detected and before any damage is caused.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide method and apparatus for detecting misalignment of platens during the clamping and molding process.
According to one aspect of the present invention, a clamp apparatus includes a frame, a first platen having a surface orthogonal to a predetermined axis, and a second platen having a surface opposing the first platen. The second platen is reciprocatable along the predetermined axis, and means are provided for reciprocating the second platen along the predetermined axis. Means also are provided for electromagnetically detecting the positions of a plurality of points on the surface of the second platen.
According to another aspect of the present invention, a mold clamp for a molding machine includes a frame, a first platen mounted on the frame having a surface with first and second opposite edges, and a second platen movable toward and away from the first platen having a surface facing the surface of the first platen with first and second opposite edges corresponding to the first and second opposite edges of the surface of the first platen. An actuating mechanism is provided for moving the second platen toward and away from the first platen, and a plurality of sensors are provided for electromagnetically detecting the respective positions of the first and second opposite edges of the second platen.
According to a further aspect of the present invention, a mold clamp for a molding machine includes a frame having a central alignment beam, a first platen mounted on the frame and disposed perpendicular to the central alignment beam, a second platen bearing on the central alignment beam, and a plurality of actuating cylinders for reciprocating the second platen along the central alignment beam. A plurality of transducer rods are mounted on the frame on opposite sides of the central alignment beam and extend parallel to the central alignment beam, and a plurality of magnets are mounted on the second platen, each of which is disposed about a transducer rod. A controller is provided for receiving a plurality of signals indicating the position of each magnet along a respective transducer rod, and determining based on the signals whether the second platen is substantially parallel to the first platen.
According to yet another aspect of the present invention, a method of determining whether a second platen is parallel to a first platen in a molding process includes the steps of: (1) emitting first and second electromagnetic interrogation pulses from a controller, (2) transmitting the first pulse to a first transducer rod fixed relative to the first platen, and transmitting the second pulse to a second transducer rod fixed relative to the first platen and parallel to the first transducer rod, (3) generating a first return signal when the first pulse reaches a magnet disposed adjacent to the first transducer rod and fixed relative to one end of the second platen, and generating a second return signal when the second pulse reaches a magnet disposed adjacent to the second transducer and fixed relative to an opposite end of the second platen, (4) transmitting each of the first and second return signals to the controller, (5) measuring the time elapsed between the emission of each pulse and the arrival of the corresponding return signal at the controller, and (6) determining, based on the times elapsed, whether opposing surfaces of the second platen and the first platen are substantially parallel.
According to still a further aspect of the present invention, a mold clamp for a molding machine includes a frame, a first platen fixed relative to the frame, and a second platen reciprocatable along a predetermined axis which lies perpendicular to the first platen and having a surface opposing a surface of the first platen. An actuating mechanism is provided for reciprocating the second platen along the predetermined axis, and a plurality of sensors are provided for electromagnetically detecting the positions of at least three points on the surface of the second platen.
According to another aspect of the present invention, a clamp apparatus includes a frame, a first platen fixed relative to the frame, a second platen movable along a predetermined axis, and an actuating mechanism for moving the second platen along the predetermined axis. An electromagnetic sensor device is provided for detecting whether opposing surfaces of the second platen and the first platen are substantially parallel.
According to a further aspect of the present invention, a clamp apparatus includes a frame, a first platen mounted to the frame, a second platen bearing on the frame and movable toward and away from the first platen, and an actuating mechanism for moving the second platen toward and away from the first platen. A sensor system is provided for detecting whether opposing surfaces of the second platen and the first platen are substantially parallel
Galt John
Kestle Martin
Fitzpatrick ,Cella, Harper & Scinto
Heckenberg Donald
Heitbrink Tim
Husky Injection Molding Systems Ltd.
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