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
1999-06-25
2001-10-09
Nguyen, Nam (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, C425S171000
Reexamination Certificate
active
06299426
ABSTRACT:
BACKGROUND AND SUMMARY OF THE INVENTION
This invention is directed to a mold and die casting apparatus including a compact core position sensor unit.
In mold and die casting systems, one or more core members of a mold body must be accurately positioned between opened and closed positions. A typical application is disclosed in copending application entitled “Threaded Actuator For Positioning Structure Subject To Intense Load” filed on Dec. 15, 1998 with Ser. No. 09/211,536 and assigned to the assignee of this application. In such application, a movable core is mounted to a core slide within a core cavity and coupled to a threaded actuator secured to the mold base or the like. The threaded actuator includes a hydraulic cylinder unit having a piston and piston rod connected to the core slide. The cylinder unit is specially constructed to establish a high locking force system between the piston rod and the cylinder thereof such that with the core appropriately located, the core is held in place under a very intense force, often greater than the cylinder motor force. In this and like applications, the accuracy of the core positioning is dependent on the accurate detection of the sensing and location of a locking member connected to the piston rod of the hydraulic cylinder unit or other prime mover. In a particularly practical and efficient system presently manufactured and sold, sensing units are connected to the hydraulic cylinder unit to detect the fully extended loaded position as well as the fully retracted position, and thereby the limits of the core slide and core. The sensing unit is attached to, and projects outwardly, from the cylinder unit. Because of various mounting systems for the hydraulic cylinder in relation to the associated equipment of the mold system, the size of the sensors must fall within certain restrictions to avoid interference with the adjoining structures. The present structure provided by the assignee uses a very small Hall effect cell based sensor which has a length of slightly less than one inch and threads into the cylinder block, with the sensing end located in accurate spaced position for detection of the loaded and the retracted positions of the actuator unit. One sensor is secured to the side of a cylinder unit to detect the forward or load position of the actuator. A second sensor is connected to the outer end of the cylinder unit to detect the retracted or release position of the actuator. One present sensor unit which has produced highly successful location detection is a integrated circuit switch using a NPN Hall effect position sensing system. The system requires a power source connection providing an output to a computer system processing the sensed signal which interconnects the output to actuate a suitable relay system. This is a relatively expensive system and employs a somewhat fragile construction and which must be adapted to each particular available voltage system. A computer interface is necessary to provide a universal connection to any type of a control system without the necessity of special conversion systems or circuitry. Although it is found to provide an exceptionally satisfactory system, the unit adds significantly to the total cost and complexity of the apparatus.
A simple sensing relay switch is preferred as it functions as a simple on/off switch and eliminates interface circuitry and expense. However, such alternative available switches providing a simple on/off switching contact have been costly and significantly only been constructed with interfering lengths, generally a minimum of three inches in length. Although the relay type switch should provide a less expensive system, the system has not in fact been less costly because of the switch cost and has not been readily accepted in many applications because of physical interference between the switch and various associated components of the mold and die casting system. Further, the available switch does not include an accurate depth setting method. The relatively large extension of the switch is also prone to damage thereof.
SUMMARY OF THE PRESENT INVENTION
The present invention provides a relatively small compact relay switch structure which can be used with minimal interference with the associated components such as water cooling lines, manifolds, platen, doors, tie bars and other parts of the mold or mold machine components as such and thereby eliminate the complex interface and interference effects, and at lesser costs than the prior art systems.
Generally, in a preferred construction, the present invention includes a relay switch having a reasonable diameter and a length on the order of inches and a maximum length on the order of two inches. The switch includes a relatively short threaded nose for mounting of the switch within the body of the position power unit or actuator with the inner end of the nose spaced slightly from the location of the locating piston or other element, with the core located in the final molding position. In the system with a rod locking system such as disclosed in the above referenced application, the locking housing is provided with an opening to receive the threaded nose connection of the switch and is preferably stepped with an innermost stop wall to accurately set the depth of the switch. The threading of the switch unit within the housing and with the body within the stepped portion minimizes the outer projection of the switch unit and insures minimum projection with respect to the mechanism and interference with the other components of the molding apparatus as such. The switch is preferably a single pole, double throw switch with a movable contact movable between two fixed contacts. The movable contact is connected to high strength magnet, which may be referred to as a target magnet. The high strength magnet is sized to be attracted by the metal piston or other moving part of an appropriate material of the core positioning mechanism in a system. The target magnet is biased by a suitable unit, and preferably an oppositely polarized, but weak magnet (which may be called a bias magnet), into spaced relation to the actuating member of the core positioning mechanism. The target magnet is mounted closely spaced from the outer face of the switch and thereby slightly spaced from the moving actuating member, which upon alignment with the target magnet overcomes the weak magnet and moves the switch. The switch includes a moving contact, and is preferably connected with a normally open contact construction for connecting to the almost universal method of core sensing and signaling the proper core position. The switch may be connected with a normally closed contact construction for any unusual design. This simple switching arrangement is found desirable as establishing the ability of the system to handle a wide range of currents and voltages, and adapts the switch for almost every wiring style available and encountered in the trade. The switch, in particular, readily covers all the common voltage sources used in national and international industrial controls of mold and die casting systems. The switch preferably has maximum contact ranges of 1 amp at 240 volts AC, 2 amps at 120 volts AC and 1 amp at 24 volts DC. Such a range will cover all common voltage sources used in national and international industrial controls and molds, and particularly conventional signal requirements such as relay interfaces and/or PLC (programmed logic control) interfaces. This versatility is particularly desirable in many sensors because they are most often wired into a control or PLC interface. A control has typical currents in the range of 0-500 milliamps at 0-24 volts DC or 0-500 milliamps at 0-240 volts AC. With common control interfaces, the normal ranges encountered are 12 or 24 volts DC and 8 volt DC NAMUR circuits.
The switch is preferably a single pole, double throw switch having three external contacts or terminals. The switch thus will allow wiring to the control of all conventional and nearly all non-conventional systems in the mold and die casting industr
Andrus Sceales, Starke & Sawall
Luk Emmanuel
Nguyen Nam
PFA Incorporated
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