Electricity: electrical systems and devices – Housing or mounting assemblies with diverse electrical... – For electronic systems and devices
Reexamination Certificate
2000-08-11
2001-11-27
Picard, Leo P. (Department: 2835)
Electricity: electrical systems and devices
Housing or mounting assemblies with diverse electrical...
For electronic systems and devices
C361S679090, C361S689000, C361S692000, C361S704000, C361S721000, C361S785000, C361S790000, C361S796000, C174S016100, C174S0170VA, C439S629000, C439S630000
Reexamination Certificate
active
06324057
ABSTRACT:
STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT
BACKGROUND OF THE INVENTION
The present invention relates to industrial controllers used for the control of industrial processes and machines, and in particular to a rugged assembly method for compact industrial controllers.
Industrial controllers are special purpose computers used for controlling industrial processes and manufacturing equipment on a real-time basis. Under the direction of a stored program, a processor in the industrial controller examines a set of inputs reflecting the status of the controlled process and changes a set of outputs controlling the industrial process. The inputs and outputs may be binary, that is on or off, or analog, providing a value within a continuous range. Typically analog signals are converted to binary words for processing.
The inputs and outputs are processed by input/output (I/O) circuitry which performs any necessary data type conversion, level shifting, isolation and amplification of the signals to and from the processor so as to be compatible with the signals required by the industrial controller. Processor and I/O circuitry for industrial control are well known in the art.
Compact industrial controllers may be produced in which the processor and the necessary I/O circuits are in a single housing. It is desirable that the base of the housing, defining its footprint when attached to the back of a cabinet, be small to conserve cabinet space. This small footprint may be accommodated by dividing the internal circuitry of the controller into multiple circuit cards stacked one on top of another.
Interconnections between the circuit cards may be accommodated by conductive connectors typically having gold plated pins necessary to communicate the low voltage logic level signals used by the processor. The multiple cards must be rigidly mounted so that vibration to be expected in the industrial environment does not cause abrasion of the gold plating layer.
In addition to holding the processor and I/O circuits, such a compact industrial controller must support terminal blocks or the like providing a means to connect the signals of the controlled equipment to the I/O circuitry. Two sets of terminal blocks separated across the front of the housing may be provided, one for input signals and one for output signals. The terminal blocks may also provide connections for line power in, user power out, and other signals known in the art.
Normally the terminal blocks will be attached directly to the circuit card holding the I/O circuitry by mechanically rigid conductors being continuations of the stampings which form part of the connector block. Forces involved in making the connections to the terminal blocks using a screwdriver or the like, therefore can be transmitted through these terminal blocks to the I/O circuit card. Unless the terminal blocks are firmly mounted, movement of the terminal blocks under such forces can cause distortion of the attached circuit card and possible damage to its printed circuitry or components.
Precise, rigid and strong mountings of each of the circuit cards and the terminal blocks against the housing are extremely difficult to achieve. “Stack-up” of tolerances between the molded components of the housing and terminal blocks prevent designs requiring close fits between each of these parts and the circuit cards.
BRIEF SUMMARY OF THE INVENTION
The present invention recognizes a hierarchy of positional relationships between the various components of the industrial controller. At the root of the hierarchy are the terminal blocks which must be solidly affixed against the housing to resist the forces incident to attachment of wires to the terminal blocks. The two terminal blocks must in turn be fixed with respect to each other and the I/O circuit card so as to prevent stresses in the I/O circuit card caused by relative movement of any of these three elements. Further, the two circuit cards must be held rigidly with respect to each other to prevent wear on their electrical interconnections. Importantly, however, there need be no direct connection between the circuit cards and the housing.
The invention therefore contemplates a “floating” mounting of the circuit cards attached to the terminal blocks and not to the housing. Rigidity is provided by the circuit cards themselves which interconnect the terminal blocks in a box-like structure. The restraint on the terminal blocks provided by their contact with the housing, channels any forces transmitted to the box-like structure into tension and compression of the circuit cards along their planes, a mode in which they are extremely strong.
Specifically, the present invention provides an industrial controller that has a housing with walls extending upward from the base and a first and second circuit card positioned within the housing. First and second terminal blocks having upper faces exposed at the upper edges of the opposite walls of the housing reveal terminal blocks for the attachment of input and output lines and hold the first and second circuit cards spaced apart, therebetween by first attachments and without requiring substantial restraining contact between the circuit cards and the housing.
Thus it is one object of the invention to provide a floating support of the circuit cards with respect to the housing eliminating the need for precise housing tolerances or stresses caused by movement of the circuit cards with respect to the housing.
The first and second terminal blocks may provide for downwardly extending legs attached to opposing edges of the upper surface of a first of the circuit cards. The second circuit card may be positioned within the housing above the first circuit card and between the terminal blocks. The first and second terminal blocks may further include at outer edges of the first and second terminal blocks, attachments to the upper edges of opposing walls of the housing. At inner portions of the first and second terminal blocks, attachments may be made to opposing edges of the process circuit card.
Thus it is another object of the invention to provide a mounting of circuit cards on the terminal blocks such as forms a rigid structure resisting torsional motion between the terminal blocks and the I/O circuit card. Downward or upward forces on the terminal blocks of the first and second terminal blocks are converted into edgewise-tensile/compressive forces on the second circuit card, a direction in which the second circuit card is extremely strong.
The industrial controller may further include a housing cover attachable to the upper edges of the upwardly extending walls of the housing and restrained from downward movement by the upwardly extending walls. The housing cover may include attachments engaging inner portions of the first and second terminal blocks.
Thus it is another object of the invention to convert downward forces on the terminal blocks such as might produce torsional movement with respect to the I/O card into downward compressive forces on the upwardly extending housing walls through the housing cover.
At least one of the first and second terminal blocks may include an upwardly exposed conductive ledge positioned above the I/O circuit card and attached via the downwardly extending legs to a receiving ground conductor of the I/O circuit card whereby the lower surface of the second circuit card may be received above the upper surface of the conductive ledge to establish a ground connection between the second circuit card and the I/O circuit card.
Thus it is another object of the invention to provide a low impedance ground connection between the two circuit cards as may be realized by the relatively robust conductors of the terminal blocks.
The housing may include a plurality of ventilation slots in the upstanding walls and the legs may provide for the passage of air from the ventilation slots between the terminal blocks and the I/O circuit card.
Thus it is another object of the invention to promote cooling airflow by removing the terminal blocks from the surface of the I/O circuit car
Baran Michael S.
Cloran Shawn D.
Chervinsky Davis L.
Gerasimow Alexander M.
Picard Leo P.
Rockwell Automation Technologies Inc.
Walbrun William R.
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