Electricity: electrical systems and devices – Housing or mounting assemblies with diverse electrical... – For electronic systems and devices
Reexamination Certificate
1999-09-27
2001-12-04
Gandhi, Jayprakash N. (Department: 2841)
Electricity: electrical systems and devices
Housing or mounting assemblies with diverse electrical...
For electronic systems and devices
C361S641000, C361S648000, C361S624000, C361S637000
Reexamination Certificate
active
06327157
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to methods and apparatus for distributing power from a power supply to one or more printed circuit boards in a computer or other electronic system that utilizes a power supply and printed circuit boards.
BACKGROUND
Numerous methods have been employed for busing power in electronic systems from a power supply to printed circuit boards.
Wires/Cables. One method has been to communicate power from the power supply to the printed circuit boards by means of discrete wires or cables. Although this method may be desirable for use in relatively low-current systems, large-current systems require wires or cables having large diameters so that the resistive and inductive characteristics of the wires or cables do not unacceptably degrade power delivery performance. Large-diameter wires and cables are problematic because they are stiff, and therefore pose routing difficulties. In addition, large-diameter cables require bulky and expensive connectors at the points of engagement between the wire or cable and the power supply or printed circuit boards. Moreover, large-diameter wires and cables degrade the ability to access other components of a system housed within the same chassis; often, such wires or cables must be removed before access to other components is possible.
Laminated Foil Straps. Another method has been to communicate power by means of straps formed with laminated copper foil layers, often with one lug on each end for engagement with the power supply or printed circuit board. One advantage of such laminated foil straps is that they have fairly good resistive and inductive characteristics even when carrying fairly large currents, and they are more flexible than wires or cables. A major disadvantage of laminated foil straps is that they are very expensive.
Traditional Bus Bars. Still another method has been to utilize rigid copper bars called “bus bars” to communicate power from one point to another within an enclosure. Among the advantages of traditional bus bars are their superior resistive and inductive characteristics and their relatively low cost. The disadvantages associated with traditional bus bars, however, are numerous: First, their rigidity creates difficulties in assembling the electronic systems that employ them. These assembly difficulties are especially apparent with regard to the tolerances they require and to the limitations they place on circuit board orientation choices. (Tolerances must be tightly maintained both in locating the bus bars within the chassis and in mounting the printed circuit boards to the chassis; otherwise, the points of engagement at either end of the bus bars will not be properly aligned with their corresponding mating points.)
Second, traditional bus bars present assembly difficulties in terms of making reliable electrical contacts at each bus bar's points of engagement. Usually, it is necessary during the assembly of such systems to use fastening tools that are capable of applying precisely measurable torque to the bolts being used to attach each bus bar to its mating point, thus insuring good electrical contact. But such tools are expensive, and are often unavailable in the field.
Third, traditional bus bars have either been coated with a layer of some kind of insulating material, or have been left exposed without insulation. Insulating the bus bars adds to the expense of the system, and leaving the bars exposed creates possible shock and short circuit hazards.
It is therefore an object of the invention to provide a bus bar system that facilitates flexibility in circuit board orientation while easing the tolerance requirements presented by prior art bus bar systems.
It is a further object of the invention to provide a bus bar system that makes reliable electrical contacts during assembly without the use of precision fastening tools.
It is yet a further object of the invention to provide a bus bar system that is less expensive to manufacture than systems utilizing insulation-covered bus bars, but that still reduces shock and hazard risks relative to systems utilizing exposed bus bars.
SUMMARY OF THE INVENTION
A power bus system according to the invention includes numerous aspects. In a first aspect, a two-piece bus bar is used in lieu of a one-piece bus bar to electrically couple a printed circuit board to a power supply. At least one member of the two-piece bus bar includes a bend. The use of the two-piece bus bar in addition to the use of the bend in at least one of the bus bars facilitates a wider choice of circuit board orientation within the chassis than is available with prior art bus bar systems. In an example embodiment, a power supply is mounted to a chassis. A power supply bus bar extends from the power supply and defines a power supply bus bar plane. A first printed circuit board is mounted to the chassis (for example via a removable printed circuit board carrier tray), and may be oriented in a plane that is not parallel with the power supply bus bar plane. A first printed circuit board bus bar extends from the first printed circuit board. At least one of the power supply bus bar or the first printed circuit board bus bar includes a bend sufficient to create a parallel relationship between a mating portion of the power supply bus bar and a mating portion of the first printed circuit board bus bar. A first fastener couples the mating portion of the power supply bus bar to the mating portion of the first printed circuit board bus bar.
In another aspect, the bend has a sufficiently large radius to facilitate proper engagement of the two pieces of the bus bar when the printed circuit board is inserted into the chassis at assembly time: In an example embodiment, the large-radius bend is included on the printed circuit board bus bar. During assembly, the power supply is installed into the chassis first. Then the printed circuit board having the printed circuit board bus bar already attached to it is inserted into the chassis. As the board is inserted, the large-radius bend causes the printed circuit board bus bar to slip underneath the power supply bus bar as desired.
In a further aspect, a second printed circuit board may be mounted to the chassis and oriented in a plane that is substantially at right angles with the power supply bus bar plane. A second printed circuit board bus bar extends from the second printed circuit board. The second printed circuit board bus bar includes a 90-degree bend and a 180-degree bend such that a mating portion of the second printed circuit board bus bar is oriented at right angles with the plane of the second printed circuit board but parallel with the power supply bus bar plane. A second fastener couples the mating portion of the power supply bus bar to the mating portion of the second printed circuit board bus bar. The unique shape of the second printed circuit board bus bar provides enhanced compliance and resilience characteristics, further alleviating tolerance difficulties. The shape also enables the mating portion of the second printed circuit board bus bar to be centered over the edge of the second printed circuit board, thus conserving space.
In a further aspect, tight tolerances required by prior art bus bar systems are eased by using adjustable fastening points to couple the two members of the two-piece bus bar together, as well as to couple the power supply bus bar to the power supply itself. An adjustable mount according to the invention may be achieved using a screw-type fastener whose screw shaft diameter is smaller than at least one inside dimension of a clearance hole formed in one of the bus bars.
In yet a further aspect, novel techniques are used to engage the printed circuit board bus bars to their respective printed circuit boards, and also to couple the printed circuit board bus bars to the power supply bus bar, thereby insuring reliable electrical contact without the need for precision fastening tools, as follows:
Interface between the printed circuit board and the printed circuit board bus bar. In an example embodiment, the fi
Babb Samuel M.
Mann Kristina L
Rock Charles Henry
Gandhi Jayprakash N.
Hart Kevin M.
Hewlett--Packard Company
Tran Thanh Yen
LandOfFree
High-current power bus system does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with High-current power bus system, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and High-current power bus system will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2597182