Geometrical instruments – Miscellaneous – Light direction
Reexamination Certificate
1999-03-18
2001-02-13
Fulton, Christopher W. (Department: 2859)
Geometrical instruments
Miscellaneous
Light direction
C033S706000, C033S710000, C065S158000
Reexamination Certificate
active
06185829
ABSTRACT:
BACKGROUND OF THE INVENTION
FIELD OF THE INVENTION
The present invention relates to position measuring devices and, more particularly, is concerned with a sensor having a two-part construction for use in translationally and rotationally operating position measuring devices, such as employed in glassware forming machines and other applications.
DESCRIPTION OF THE PRIOR ART
In the production of hollow glass articles using a press-and-blow process in a so-called I.S. glassware forming machine, gobs of molten glass with predetermined mass are successively separated from a stream exiting a feeder, placed into a forming tool of the forming machine, and shaped into a blank, also referred to as parison, by a movable plunger penetrating into the gob. The blank can then be further processed in the glassware forming machine. The plunger is attached on a piston rod of a piston/cylinder unit of the machine which cooperates with a device for the continuous measurement of the position of the plunger during its stroke. The continuous measurement of plunger position is important since, based thereon, the pressing procedure is controllable and conclusions regarding the level of filling of the mold, the penetration depth of the plunger, and thus the quality of the blank can be drawn from which corrective measures can be derived.
An apparatus of the above type is known from German Patent Document No. DE 34 01 465 C1. In the known apparatus the piston rod carries an annular core as an actuation element for changing the inductance of a coil. The coil is disposed in an annular socket in an upper portion of a cylinder directly below the piston rod support. This construction has the disadvantage that measuring technology can only determine values within a short distance of the piston stroke and a galvanic plug connection is required which, when changing the cylinder, must be detached and fastened again. In view of the limited space, it is difficult to provide the plug connection with the cable.
Such plug connections which are also included in devices known from U.S. Pat. No. 5,139,559 and European Patent Document No. EP 488 136 A2, suffer from a susceptance to failure. In the presence of accumulating dirt, they do not operate faultlessly and can even be destroyed. All known sensors of such plunger position measuring devices require considerable mechanical expenditures.
SUMMARY OF THE INVENTION
The present invention overcomes the aforementioned problems by providing a sensor in a position measuring device having a two-part construction wherein the two parts are inductively coupled to one another but galvanically and mechanically isolated from one another which avoids the necessity to use a galvanic plug connection while providing a compact, cost-effective arrangement with high precision, which, in spite of limited space, permits the ready problem-free exchange or replacement of a casing or cylinder supporting one of the two parts.
Accordingly, the present invention is directed to a sensor in a position measurement device for employment with a machine having a base, a movable operating member, a casing mounted to the base and an actuation member mounted to the movable operating member and disposed adjacent to the casing to undergo movement relative thereto with the movable operating member. The sensor, being adapted for providing continuous measurement of the position of the actuation member as it moves relative to the casing and thereby of the position of the movable operating member, is structured as a two-part oscillator.
The first part of the oscillator includes a resonance circuitry formed of a coil and a capacitor. The coil is supported on the casing of the machine. The capacitor has first, second and third capacitor elements. The first and second capacitor elements are supported on the casing of the machine in a fixed relation to one another. The third capacitor element is supported on the actuation member of the machine and movable therewith relative the first and second capacitor elements such that the resonance circuitry has a resonance frequency which is variable in proportion to the change of capacitance of the capacitor in response to the change of the position of the actuation member relative to the casing and thereby of the third capacitor element relative to the first and second capacitor elements as caused by movement of the movable operating member of the machine.
The second part of the oscillator is provided on the base of the machine such that the second part of the oscillator is galvanically isolated and mechanically separated from the first part of the oscillator. The second part of the oscillator includes a coupling coil supported on the base of the machine adjacent to and inductively coupled with the coil of the resonance circuitry of the first part of the oscillator so as to produce an output oscillation frequency proportional to the resonance frequency of the resonance circuitry.
Due to the sensor construction in the two parts, the resonance circuitry can be introduced compactly into the casing and actuation member, such being for instance a piston/cylinder unit, of the machine without the use of galvanic connectors so that the ready exchange or replacement of the cylinder of the unit is possible. A further advantage is that the measuring device can be produced cost-effectively with high accuracy being attained in the position detection.
In a practical embodiment of the invention, the machine base is a stationary mounting plate disposed in a glassware forming machine and the coupling coil of the oscillator or sensor is disposed on the mounting plate. The mounting plate also includes connections for supplying the electric energy required for the operation of the oscillator as well as for conducting out the output oscillation frequency signal of the coupling coil. In an opening of the mounting plate is disposed the coupling coil while in an opening in the bottom of a cylinder of a piston/cylinder unit is disposed the coil of the resonance circuitry in opposing relation to the coupling coil. On the mounting plate is also detachably attached the cylinder of the piston/cylinder unit with the resonance circuitry.
Further, in the practical embodiment of the invention, on the inside of a tube for delivering cooling air to a plunger, over which the hollow piston rod is translationally movable, is disposed the resonance circuitry coil whose feed lines are connected to two large capacitor areas of equal size, which are also disposed on the inside of the cooling air tube and extend over the length of the range of influence of the hollow piston rod. All galvanic connectors are thus attached permanently on a stationary mounting plate of the machine and do not need to be touched when exchanging or replacing the piston/cylinder unit. The cooling air tube and a flange part, fixable on the cylinder bottom, are preferably implemented integrally by an insulating material, for example a ceramic material.
In a preferred modification of the measuring device another tube is located within the cooling air tube and the resonance coil, its feed lines and the capacitor areas are disposed in the interspace between the two tubes. All of these parts are, in turn, affixed by adhesion with the flange part fixed on the cylinder bottom to form a hermetically sealed unit.
The oscillator output signal of the coupling coil is preferably supplied to a frequency measuring unit to which an evaluation electronics is connected for detecting the position of the plunger connected to the piston rod. The power supply of the oscillator and the conducting-out of the oscillator output voltage preferably takes place via a coaxial cable with the inner conductor and shielding assuming the DC power supply, and the oscillator output voltage, after having been conducted out, is superimposed onto the power supply DC voltage.
These and other features and advantages of the present invention will become apparent to those skilled in the art upon a reading of the following detailed description when taken in conjunction with the drawings
Flanagan John K.
Flanagan John R.
Flanagan & Flanagan
Fulton Christopher W.
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