US 3663925 A
An electrical connector for interfacing a PC (printed circuit) board with external circuits. A nonconductive core, formed to engage the edge of the PC board adjacent to the printed circuit terminals, receives two rows of opposed contact springs, each spring having a bifurcated portion in the core for receiving a contact pin of an external circuit and a base portion extending outwardly for engaging either side of the circuit board at selected terminals. The bifurcated portions of each spring are inwardly inclined from their respective ends to form pin contact points developed from each other along their length. A nonconductive cover removably fitted over the core and springs provides accessibility for spring replacement and protection against contact pin damage.
Description (OCR text may contain errors)
United States Patent Proctor  Assignee: The United States of America as represented by the Secretary of the Navy I22] Filed: May 20, I970 l2l| Appl. No.: 39,693
 U.S.Cl. ..339/65,339/176 MP  Int. Cl. ..I-I0lr 13/62  Field ofSearch ..339/l7, 65,66,176
 References Cited UNITED STATES PATENTS 3,413,594 11/1968 Fernald et a1. ..339/176 MP 3,482,201 12/1969 Schneck ..339/14 2,701,346 2/1955 Powell ..339/17 LM 51 May 16, 1972 FOREIGN PATENTS OR APPLICATIONS 1,232,014 4/1960 France ..339/17 LC Primary Examiner-Joseph I-I. McGlynn An0rneyR. S. Sciascia and Henry Hansen 1 57 1 ABSTRACT Ai elcctrical connector for interfacing a PC (printed circuit) board with external circuits. A nonconductive core, formed to engage the edged the PC board adjacent to the printed circuit terminals, receives two rows of opposed contact springs, each spring having a bifurcated portion in the core for receiving a contact pin of an extemaI circuit and a base portion extending outwardly for engaging either side of the circuit board at selected terminals. The bifurcated portions of each spring are inwardly inclined from their respective ends to form pin contact points developed from each other along their length. A nonconductive cover removably fitted over the core and springs provides accessibility for spring replacement and protection against contact pin damage.
9 Claims, 2 Drawing Figures Patented May 16, 1972 3,663,925
r INVENTOR. RICHARD D. J. PROCTOR BY aj TTORNEY ELECTRICAL CONNECTOR STATEMENT OF GOVERNMENT INTEREST BACKGROUND OF THE INVENTION The present invention relates generally to electrical connectors, and more particularly to electrical connectors for interfacing PC boards to external electrical circuits.
PC boards used in high-density stacked arrays usually have circuits on both sides leading to equally spaced terminals along a straight edge of the board which is accessible for external wiring connections. Prior art connectors are usually inserted over the edges of the PC boards for interconnecting the terminals with contact pins of external circuits. Connectors of the type to which the present invention is related usually contain contact springs positioned to wipe against the terminals when inserted on the edge of the PC board and in various manners wipe against the contact pins. The precise configuration of the contact springs within the connector is critical as it must assure positive, low resistance, non-interruptable electrical continuity. These criteria are particularly critical in avionic equipment demanding high degrees of reliability and performance in aircraft environments. The prior art connectors are usually constructed with the contact springs permanently embedded in a single plastic mold making them inaccessible for replacement if damaged during assembly to the PC boards or upon receiving the contact pins or inaccessible for soldering the contact springs to the PC board terminals if desired. Also, prior art connectors frequently caused circuit interruptions between the contact springs and the PC board terminals and the contact springs and the contact pins when subjected to vibrations at the resonance frequency of the contact spring.
SUMMARY OF THE INVENTION Accordingly, it is a general purpose and object of the present invention to provide a novel and improved electrical connector for interfacing a PC board with external electrical circuits which is capable of maintaining positive and continuous electrical connection during operation in adverse environmental conditions. Another object is to provide an electrical connector in which the contact springs contained therein are accessible for individual replacement before or after assembly to the PC board while maintaining shrouded or so-called closed entry about the springs for protecting them from contact pin and other type damage. Still another object of the invention is to provide an electrical connector which is relatively simple in construction, inexpensive and easily manufactured.
Briefly, these and other objects of the invention are accomplished by a unique configuration and positioning of contact springs in a nonconductive core and cover. The springs are positioned on opposite sides of a nonconductive core with base portions extending outwardly for engaging the sides of the PC board at selected terminals. A cover having contact pin access holes adjacent each spring is removably positioned over the core and springs to provide limited access or closed entry to the springs by the contact pins. Each spring includes a bifurcated portion and a base portion extending in opposite directions for engaging, respectively, an external circuit contact pin and a PC board terminal. The arms of the bifurcated portion incline toward each other from the base portion at different angles to form contact points displaced from each other along their length, and then incline outwardly from the contact points to terminate at the cover access holes. Alignment pins extending from the core are formed to be inserted into correspondingly aligned holes in the PC board to insure contact spring-terminal alignment.
BRIEF DESCRIPTION OF THE DRAWING FIG. 1 is a fragmented view of a preferred embodiment of an electrical connector according to the invention juxtapositioned for electrically interfacing a typical PC board with a contact pin block; and
FIG. 2 is a cross-sectional view of the electrical connector, PC board and pin block taken along the line 2-2 of FIG. 1.
DESCRIPTION OF THE PREFERRED EMBODIMENT Referring to the drawing there is shown an electrical connector l0 edge-connected to a typical PC board 11 and juxtapositioned for receiving a contact pin block 12. The board 11 includes a plurality of discrete printed circuits 13 on either side of an electrically nonconductive card 14 terminating in parallel striped contact terminals 16 spaced along and normal to the length of a straight edge of card 14. The straight edge of card 14 is formed with a projecting rib 17 along the length thereof intermediate its side. The pin block 12 includes a plurality of parallel contact pins 15 electrically connected to external circuits, not shown. Of course, the pins 15 may be separate from each other for individual insertion into the connector 10. The pins 15 are preferably of square cross-section for affording line contacts in the connector 10. The structure by which this is accomplished will become apparent hereinafter.
Electrical connector 10 comprises a nonconductive core 18 having two parallel flat sides and a groove 19 along the length of one straight edge and intermediate the sides formed for removably receiving rib 17 of board 11. A pair of parallel alignment pins 21 extending from the board-engaging edge are formed to slide into correspondingly positioned alignment holes 22 in card 14 for insuring proper orientation of connector 10 with the PC board 11.
Each side of core 18 is formed with a plurality of spaced recesses 23 for receiving contact springs 24. The recesses extend from the contact pin-engaging edge of connector 10 and terminate short of the board-engaging edge.
Each contact spring 24 is constructed of an electrically conductive, preferably flat, resilient material with a base portion 26 and a bifurcated portion 27. Portion 27 is positioned in the recess 23 with the connected ends of the bifurcations or arms adjacent to the terminated end of recess 23. The arms incline toward each other from their joined ends at different angles to form line contacts 28 and 29 displaced from each other along the length, and then incline outwardly from the line contacts to terminate at the contact pin-engaging edge of core 18. It should be noted that, while the two arms of each portion 27 are substantially equal, the lateral forces applied at line contacts 28 and 29 when confronting flat sides of a contact pin 15 is inserted will produce different resonance frequencies in each arm. In this manner no single vibration frequency can cause circuit interruption between contact pin 15 and spring 24.
The base portion 26 of each spring 24, commencing at the joinder of the bifurcated portion 27, extends outwardly from the sides of core 18, turns inwardly beyond the board-engaging edge of core 18, and finally turns outwardly to form a line contact with a PC board terminal 16 when PC board 11 and connector 10 are fully engaged. It will be noted that the base portion 26 where it is in line contact with terminal 16 is exposed and readily accessible for soldering to insure positive uninterruptable electrical connection between a printed circuit l3 and a corresponding contact spring 24.
The contact springs 24 are retained in recesses 23 by an electrically nonconductive cover 32 removably positioned against the sides and contact pin-engaging edge of core 18. Cover 32 includes a plurality of openings 33 registering with the distal ends of respective bifurcated portions 27 of spring 24 providing thereby limited access or closed entry to connector 10 by the contact pins 15. Openings 33 are flared outwardly to guide slightly misaligned contact pins 15 of pin block 12 into the connector 10 without damaging springs 24.
From the foregoing description, some of the many advantages of the present invention should now be apparent. For example, an extremely versatile electrical connector is provided in which the contact springs may be soldered to the terminals after assembly to a PC board in order to obtain uninterruptable mechanical interconnection, individual contact springs in an operational connector may be removed or replaced after assembly to a PC board simply by unsoldering the base portion of the spring from the PC board terminal, sliding the cover off of the core, and extracting the spring. The inventive connector is also capable of maintaining continuous electrical connection between contact springs and the contact pins by imparting different resonance frequencies to the opposite arms of the bifurcated portions. The connector also affords a closed entry for protecting the contact springs from physical damage caused by misaligned contact pins of a pin block.
It is understood, of course, that the foregoing disclosure relates to only one embodiment of this invention and that many modifications and variations in the details may be made therein without departing from the spirit and scope of the invention as set forth in the appended claims.
What is claimed is:
1. An electrical connector for interfacing terminals along one edge of a printed circuit board and contact pins having external circuits connected thereto, comprising:
an electrically nonconductive core having opposite edges,
one edge being formed to edge-connect with the printed circuit board, and one side with a recess formed therein extending from adjacent said one edge to the other edge;
a contact spring having bifurcated arms positioned in said recess, the distal ends of said arms being adjacent to said other edge of said core, and a base portion extending from said one edge of said core and forming a contact point thereon engageable by a selected one of the terminals of the printed circuit board; and
an electrically nonconductive retaining means removably connected to said core and said spring for retaining said spring within said recess.
2. A connector according to claim 1 wherein said arms are inclined toward each other from the base portion and from the distal ends to form contacts displaced from each other along the length of said arms.
3. A connector according to claim 2 further comprising:
an alignment pin held in said core and extending outwardly from said one edge of said core and positioned to insert in a corresponding hole in the one edge of the printed circuit board.
4. A connector according to claim 3 wherein said retaining means comprises:
a cover slidable over said edge of said core for retaining said spring in said recess and having an opening therein registering with the distal ends of said arms for receiving a contact pin therebetween.
5. An electrical connector for interfacing a printed circuit board having a plurality of terminals along a ribbed edge thereof and a contact pin block having a plurality of pins connected to discrete external circuits, comprising:
an electrically nonconductive core having opposite edges, one edge being formed to edge-connect with the ribbed edge of the printed circuit board, and parallel sides each having a plurality of recesses formed therein extending from adjacent said one edge to the other edge;
contact springs each having bifurcated arms positioned in respective ones of said recesses, the distal ends of said arms being adjacent to said other edge of said core, and each having a base portion extending from said one edge of said core and forming a contact point thereon engageable by a selected one of the terminals of the printed circuit board; and
an electrically nonconductive retaining means connected to said core and said springs for retaining said springs within said recesses.
6. Apparatus according to claim 5 wherein the arms of each of said springs are inclined toward each other from the base portion and the distal ends to form contacts displaced from each other along the length of said arms.
7. A connector according to claim 6 wherein said retaining means comprises:
a cover slidable over said other edge of said core for retaining said springs in said recesses and having openings therein registering with the distal ends of respective ones of said arms for receiving the pins of said contact pin block therebetween.
8. A connector according to claim 7 further comprising:
a plurality of alignment pins held in said core and extending outwardly from said one edge of said core and positioned to insert in corresponding holes in said one edge of the printed circuit board.
9. A contact spring for interconnecting a terminal of a printed circuit board and a contact pin, comprising:
a base portion formed to be connected to a terminal of the circuit board; and
a pair of bifurcated arms extending from said base portion, the arms being inclined toward each other from their base portions and from their distal ends, the apices formed thereby being displaced from each other along the length of said arms.