|Publication number||USRE34084 E|
|Application number||US 07/705,488|
|Publication date||Sep 29, 1992|
|Filing date||May 24, 1991|
|Priority date||Feb 13, 1989|
|Publication number||07705488, 705488, US RE34084 E, US RE34084E, US-E-RE34084, USRE34084 E, USRE34084E|
|Inventors||Rocco J. Noschese|
|Original Assignee||Burndy Corporation|
|Export Citation||BiBTeX, EndNote, RefMan|
|Patent Citations (5), Referenced by (27), Classifications (8), Legal Events (2)|
|External Links: USPTO, USPTO Assignment, Espacenet|
The present invention is directed to electrical contact springs, particularly to those used for establishing and maintaining electrical connections between circuit boards.
When transmitting signals from board to board in an electrical circuit, it is essential that the integrity of the signals be protected or shielded from interfering with each other through noise, etc. Additionally, the length of the signal circuit must be relatively short to avoid disturbances of signal integrity related to length of connector.
Prior art patents directed to electrical connectors include U.S. Pat. Nos. 4,161,346, 4,505,529 and 4,752,231.
U.S. Pat. No. 4,161,346 is directed to an electrical connector for interconnecting electrical circuits on two electronic circuit boards involving surface to surface contact between generally parallel surfaces. The patent discloses a connector element having a symmetrical, sinuous shape including a spring section for exerting a determined contact force and establishing the electrical connection. In addition, the connecting element is provided with a separate shorting beam into connector opposed ends and the connecting element to provide a shorter electrical path and to act as a spring for retaining the contact element within its housing.
U.S. Pat. No. 4,505,529 relates to a connector for electrically interconnecting printed circuit boards in the form with three elongated beams extending between contact surfaces with the configuration of the contact element being such that it buckles under compression forces to provide spring forces.
U.S. Pat. No. 4,752,231 is directed to an electrical connector including a rigid insulating housing bolted between parallel circuit boards and having electrical connectors located within and positioned by the rigid housing for establishing electrical contact between the circuit boards. The connectors themselves are in the form of semi-elliptic springs having outwardly projecting tips for establishing contact with opposing portions of the circuit board.
U.S. Pat. No. 4,778,404 is of interest and is directed to a spring terminal having an intermediate spring portion form of spring sections joined at their adjacent ends to form a zig zag configuration. The terminal is held in a fixed position and is generally adapted for use in difficult environmental situations where mating connector members must be fully sealed.
A commercially available electrical connector includes telescoping, longitudinally connected spring loaded elements in the form of "pogo stick" for providing spring-biased connectors.
Each of the foregoing devices involves complex connector constructions including multiple components in several cases and complicated assembly techniques. Additionally, the block members used for holding and positioning the connectors also have intricate designs to accommodate assembly and functioning of the connectors. The complexities of design, assembly, and operation of these connectors are drawbacks in electronic circuit board devices having a multitude of connections and where available space is limited and are counterproductive as they increase opportunities for loss of signal integrity.
The present invention is directed to an electrical contact spring used for interconnecting parallel circuit boards in which the spring is received and positioned in a metal block between the circuit boards. The spring connector consists of a single metallic element wound in the form of a spiral about its longitudinal axis and providing for electrical contract at its opposite ends positioned between parallel circuit boards and having longitudinal resiliency to establish firm spring electrical contact between the circuit boards. Additionally, the contact spring tend to expand radially when compressed to promote firm engagement between the spring itself and the cylindrical walls of matrix or holding block used for receiving and positioning a multitude of contact springs.
The contact spring according to the present invention has the following advantages over the prior art. The spring is fabricated from a single blank by rolling the blank into a spiral and coining the tips to provide surface contact between opposed circuit board pads. For assembly, the connectors are inserted into cylindrical bores or holes in a holding block and are retained within the bores as the springs expand radially. The spring members are resilient and return to the original position after compression forces are released and they are not permanently deformed.
A metal block containing electrical contact springs of the present invention is placed between parallel circuit boards and provides a means of transmitting shielded signals from board to board. For transmitting signals, a contact spring is placed in an insulating sleeve and located in a hole or bore in the metal block. The insulated signal spring is surrounded by shielding or grounding circuits in order to protect the signals through the metal block interface from interfering with one another with noise and so forth. The shielding or grounding circuits are insulated contact springs fitted in holes through the metal block located around the signal carrying connectors and serve to protect signals from interference.
A contact spring according to the invention provides a signal circuit of relatively short length through the connector block. The short length of the signal circuit reduces the opportunity for disturbing signal integrity.
It is an object of the invention to provide a one piece electrical contact spring which is formed by rolling a one piece blank spiral form to provide a longitudinally and laterally resilient contact spring.
Another object of the present invention is to provide an electrical contact element in the form of a spiral spring which yields longitudinally to provide spring contact between opposed circuit boards and yields radially to provide firm contact positioning the spring within its carrier member.
A further object of the invention is to provide an arrangement for transmitting shielded signals between circuit boards through a signal circuit connector of short length minimizing the opportunities for disturbing signal integrity.
Another further objects of the invention will occur to those skilled in the art with an understanding of the detailed description of the invention or upon employment of the invention in practice.
A preferred embodiment has been chosen for illustrating and describing the invention and is shown in the accompanying drawing in which:
FIG. 1 is side elevational view partly in section showing the spring action electrical connectors held in position in a connector retaining block between circuit boards.
FIG. 2 is a plan view of a blank used in forming a spring connector according to the present invention.
FIG. 3 is a detailed perspective view of an end or tip of a connector according to the .[.presenting.]. .Iadd.present .Iaddend.invention showing the formation of a contact surface.
FIG. 4 illustrates the spring connector in a free state.
The present invention is used with electronic components such as circuit boards in which a multitude of electrical connections must be established between components. As shown in FIG. 1, a sub-assembly of an electrical device 10 including .[.an.]. .Iadd.a .Iaddend.PC board 12 and a back plane 14 are generally parallel and are fitted with pads 16 for establishing electrical connection therebetween. A retaining block 18 is a conductive metal and has a multitude of holes 20 therein for receiving connectors 22 according to the invention. In one case, a signal connector 22a is placed within an insulating plastic or other dielectric sleeve 24 for insertion into the retaining block. In another case a ground connector 22b is placed within the retaining block bore as a ground connection between PCB pads, retaining block, and back plane.
In order to protect transmitted signals from interference, each signal connector 22a is surrounded by ground connectors 22b such that signal connectors are spaced from each other in length and width of the retaining block by means of a ground connector. The surrounding ground connectors and the metal retaining block provide such signal integrity protection.
A connector 22 according to the present invention, comprises a spiral wound longitudinally compressible spring connector for establishing electrical contact between spaced electronic board members. The spaced boards have a number of corresponding electrical surfaces or pads 16 which require contact by a multitude of connectors. The connector 22 is a one-piece spiral-would coil of conductive material having longitudinally spaced contact tips 26 for establishing contact with PCB and back plane pads 16. Additionally, opposite tips flex independently of each other. It will be observed that each end or tip 26 of the connector is rolled or coined in the form of a dome (FIG. 3) 28 to provide a contact surface for purposes of establishing an electrical connection. In another aspect of the invention, the connector expands radially of its longitudinal axis as it is compressed more firmly to secure the connector within its receiving bore of the metal block. This has an advantage in that it is not necessary to press the spring uniformly from both ends. Indeed, the spring connector may be compressed from one end and will expand radially into firm and immovable contact with its receptacle. This has the advantage of allowing flexibility in assembling circuit board members from either end of the spring connector in whatever sequence is desired.
FIG. 2 illustrates a developed blank 30 from which the spring connector is fabricated. The blank is generally Y-shaped including a rectangular base portion 32 and a pair of outwardly divergent arms 34 projecting from one side of the base. Any suitable angle of divergence α may be selected and in the embodiment shown in FIG. 2 the angle is 30°. The outer ends of each arm are trimmed to form tips 36 which become the outer extremities of the connector in rolled form. Preferably the blank is formed of a suitable conductive metal such as berylium .[.cooper.]. .Iadd.copper .Iaddend.of high tensile strength and a thickness of approximately 3 to 4 mils. The berylium .[.cooper.]. .Iadd.copper .Iaddend.blank may be plated with an outer gold layer over a nickel base. The spring is formed by rolling into a tight spiral having at least 3 complete coils when placed in a 30 mil diameter .[.gage.]. .Iadd.gauge.Iaddend..
As shown in FIG. 3, the tip 36 at each end of the spring is coined over forming a dome-shaped contact area 28 to assure an electrical connection based on the surface of the spring and not a tip or edge.
FIG. 4 illustrates the spring connector in free form including a central or waist section 38 and longitudinally projecting spring action arms 40. Each of the tips deflects independently of the other a distance of approximately 10 percent of the overall length between tips of the connector with no set. Additionally, the spring connector is capable of a reduction in waist diameter d to approximately 0.8d to accommodate insertion in a bore 20 or sleeve 24 of the retaining block while maintaining spring action of each of the contact arms. A specific form of contact spring has the following approximate dimensions in inches: overall length (ol) 0.208; waist length (wl) 0.090; waist diameter free state (d) 0.036; waist diameter in service 0.030; and contact arm deflection (dfl) of 0.020 under a force of 50-100 grams without set. .Iadd.As can be seen from FIG. 4, when the spring is rolled into a spiral, the upper and lower arms 40 of the Y-shape extend away from the central section 38 with two opposite twists. The upper arm has a left hand twist and the lower arm has a right hand twist. .Iaddend.
A significant advantage of the invention is the relatively short length of the signal circuit through the connector block made possible by the short overall length of the connector reducing the opportunity for disturbing signal integrity through factors related to length of signal connector circuit.
It will be understood from the above description that the contact spring is formed using conventional materials and provides a connector of considerable advantage when compared to springs of the prior art.
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|U.S. Classification||439/66, 439/245, 439/82|
|Cooperative Classification||G01R1/06738, G01R1/06716, H01R12/714|
|Apr 4, 1994||FPAY||Fee payment|
Year of fee payment: 4
|Apr 8, 1998||FPAY||Fee payment|
Year of fee payment: 8