1. Field of the Invention
The invention generally relates to surface mount connectors and, more specifically, to a keyhole surface mount connector.
2. Description of the Prior Art
Published Patent Application 20060094283 to James discusses a switch with insulation displacement connectors. The application discloses vertical keyhole connectors mounted on the body of a switch. The keyhole connectors include keyhole shaped openings that define a pair of parallel tines that straddle a slot. A slight edge being suggested, for example, in the keyhole connector 16 where the larger upper, generally circular opening transitions into the lower vertical slot. However, while the application shows a keyhole shaped connector there is no pronounced cutting barb or any other edge irregularities that perform multiple functions. U.S. Pat. No. 7,026,559, also issued to James, contains a similar switch construction as disclosed in the published '283 application.
Quintanilla U.S. Pat. No. 7,186,132 discloses an electrical and electronic connector that includes keyhole openings. This patent also suggests a modest cutting edge as the larger opening transitions to the elongated slot into which a cable is ultimately forced into. A lever is used to urge buttons to advance the wires to their desired positions. However, neither the published application to James nor the Quintanilla patent teach or suggest keyhole connectors that can be surface mounted on printed circuit boards nor multi-function edge irregularities.
U.S. Pat. No. 6,616,4762 Moritz teaches and electrical plug-in connector formed as a sheet metal stamping including a keyhole connector formed of sheet metal and folded as shown to provide two spaced keyhole contacts. However, the flat portions appear to be recessed and arranged in an electrical plug connector of the type shown that would prevent surface mounting. Additionally, this patent, as the previous ones, teaches what appears to be a modest cutting edge at the transition point where the larger circular opening meets the elongated slot.
U.S. Pat. No. 4,037,905 to Lucas discloses a no-strip electrical connector including an aperture and a slot. This connector also discloses a simple modest cutting edge at the transition point. While the conductive members have a generally flat outer base there is no teaching that the connector is surface mountable. Nor does the patent teach, as the previous references failed to teach, cutting barbs that project inwardly into the space at the transition points and optional additional surface or edge irregularities or features provided on the opposing edges of the longitudinal slots that perform additional functions such as enhancing contact and retaining the conductors in place after insertion.
An electrical connector, electrical terminal and a method of making electrical connection are disclosed in U.S. Pat. No. 3,990,762 issued to Lemesle. This patent, as well, teaches a keyhole connector. While the transition points appear to provide a somewhat sharp edge these appear to be curved or rounded. In other respects, the keyhole connectors shown this patent share common features with the other prior art connectors. There is no teaching nor suggestion that the keyhole connectors disclosed in this patent are capable of being surface mountable.
U.S. Pat. No. 2,738,479 to Gibson discloses a plural wire stripper and electrical connector. This patent teaches a pair of sidewalls that appear to be inwardly tapered in the direction away from the larger opening. The keyhole connector disclosed in this patent, therefore, shares the same features as in the other patent references, none of which teaches such connectors designed to be surface mounted nor provided with edge features, at and beyond the transition points, that are useful in stripping insulations, making contact with electrical connectors and ensuring that secure mechanical and electrical connections are maintained over time.
Accordingly, it is an object of the present invention to provide a surface mount keyhole electrical connector that does not have the disadvantages or limitations inherent in prior art keyhole connectors.
It is another object of the present invention to provide a surface mount keyhole electrical connector as in the previous objects that is simple in construction and inexpensive to manufacture.
It is still another object of the present invention to provide a surface mount electrical connector that is suitable for surface mounting on a printed circuit board.
It is yet another object of the present invention to provide a surface mount electrical connector as in the previous objects that can reliably strip or remove insulation to expose the electrical conductors within the insulated conductors after the contact has been surface mounted on a printed circuit board.
It is a further object of the present invention to provide a surface mount keyhole electrical connector that can be used to electrically and mechanically terminate an insulated conductor.
It is still a further object of the present invention to provide a surface mount keyhole electrical connector of the type under discussion that is suitable for terminating both single insulated conductors as well as coaxial cables that include metallic shields.
It is yet a further object of the present invention to provide a surface mount keyhole electrical connector that can be used with an inline box surface mount connector for mechanically and electrically terminating both the shielded portion of a coaxial cable as well as the center conductor thereof.
It is an additional object of the present invention to provide a surface mount electrical connector that can be used with a suitable insertion tool for moving an insulated conductor from a position in which the insulation is not yet displaced to a location in which the insulation is displaced, stripped or removed to expose the conductive wire or strands to provide contact with the conductive portions of the conductor.
It is still an additional object of the present invention to provide a surface mount keyhole electrical connector as in the previous objects in which keyhole apertures are provided that extend along insertion directions that are either parallel or perpendicular to the circuit board.
In order to achieve the above objects, as well as others that will become evident to those skilled in the art, a surface mount electrical keyhole connector comprises a generally flat mounting portion suitable for surface mounting on a printed circuit board (PCB) and at least one contact portion generally normal or perpendicular to said flat mounting portion, said at least one flat contact portion being provided with an aperture generally in a shape of a keyhole that defines a longitudinal axis and includes an upstream open region dimensioned to receive with clearance an insulated conductor having a metallic conductor generally having a diameter d1 surrounded by an outer insulation coating and a downstream elongated slot formed by generally parallel opposing edges substantially parallel to said axis of symmetry and spaced from each other a distance h that is less than said diameter d1, said generally circular and opposing edges meeting at intermediate transitions points where said enlarged upstream open region transitions with said downstream elongated slot. The edges at said transition points form insulation cutting means for cutting or stripping insulation off an insulated conductor. Retaining means are provided for retaining a conductor forced into said downstream elongated slot to prevent an insulated conductor from moving upstream back into said upstream open region, said opposing edges of said elongated slot downstream of said transition points serving to make positive contact with the conductive wire or wires within an insulated conductor after the conductor is urged downstream into and is fully seated within said elongated slot.
Those skilled in the art will appreciate the improvements and advantages that derive from the present invention upon reading the following detailed description, claims, and drawings, in which:
Referring specifically to the Figures, in which identical or similar parts are designated by the same reference numerals throughout, and first referring to
In accordance with the broader aspects of the invention an electrical keyhole connector suitable for surface mounting includes a generally flat mounting base portion 12a parallel to an of symmetry As (
Each contact portion 12b, 12c is provided with an aperture or opening K generally in a shape of a keyhole the axis of symmetry of which is generally parallel to the connector axis Ak in the embodiment (
The generally circular and opposing edges E1 and E2, E3 meet at intermediate transition points K3 where the enlarged opening region K1 transitions with the elongated slot K2. The transition points K3 form insulation cutting edges for penetrating the insulation and cutting and stripping the insulation off of an insulated conductor as it is forced from the circular region K1 to the elongated slotted region K2.
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In order to assure that all the insulation proximate to the contact regions of the center conductors and/or conductive shields is removed and good electrical contact is assured the spacing between the opposing edges of the keyhole slots are reduced in relation to the anticipated diameters of the center conductors and the conductive shields, respectively. This dimensional reduction is exemplified in the following table:
The reduction should be by at least 0.010″. The slot reduction should also be at least 10% of the conductor dimensions. Excessive reduction can damage the conductors. However, the maximum reduction should be 30% and optimal reduction should be in the range of 12-25%. A reduction of 20% provides an effective compromise to maintain the integrity of the conductors while insuring reliable contact between the conductors and the connectors. This also allows the same connectors to accommodate more than one AWG wire size.
Referring to
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Thus, a feature of one embodiment according to the invention is the provision of irregular edge configurations past the two sharp cutting edges where the insulation is cut or stripped. As the stripped wires (coax, solid or stranded) are pushed further, they are compressed between the groove opposing edges to make electrical contact as described. There is preferably a slight angle in the groove side walls to help drive the wire deeper into the slot as time goes on and not back out in a direction of the enlarged circular region.
The connector in accordance with the present invention can be defined as an insulation displacement connector (IDC) bypassing the need to strip the wires of insulation in a separate step prior to termination.
The surface mount connector in accordance with the present invention can be used, as noted, to mechanically and electrically terminate a coaxial cable or electrical wire without stripping the insulation. A lower wire insertion force is needed with this connector than with standard IDCs because of the two tandem step configuration, namely first cutting the insulation with sharp barbs for cutting just the insulation at the beginning of the groove then pushing the wire downstream to make the electrical connection. Conventional IDCs strip, cut and clamp the wires with the same blades and often dig into the metal wires causing higher insertion forces. With this invention a wire can be inserted from the side using a modified needle nose pliers rather than using special tool, pushing the wire from the top of the connector and compressing the PCB (printed circuit board). By tapering the walls of the groove the side walls connector has the feature of pushing the wire deeper into the connector rather than having the forces of the cutting blades backing up the wire. The retaining hooks or barbs (KS) at the beginning of the grooves also prevent the conductor from moving backwards. Finally, the keyhole connector 10, 18 can be plated, such as with gold and the wire contact area (slot edges) will only impart sliding friction of the wire wearing a plating. The standard IDC contact area plating can be worn away because the contact area will also be used for stripping the insulation, cutting into the wire or cutting strands of wire.
The first keyhole barbs cut into the wire approximately 0.005 inches, while stripping away the insulation. As the stripped wire proceeds into the keyhole slot, it conforms to the keyhole slot which is approximately 0.015 inches narrower than the wire diameter. This narrow passage conforms and compresses the wire in the slot to ensure good electrical contact.
The horizontal version of the keyhole connector provides wire insertion from the side with a pair of modified pliers while the vertical version requires an insertion tool that applies a downward force Fv on the wire which will result in a compressive load on a circuit board. However, because most of the load is to displace the soft insulation the forces executed on the PCB can be controlled or limited to prevent damage to the board.
Keyhole connectors 10″ (
The foregoing is considered as illustrative only of the principles of the invention. Further, since numerous modifications and changes will readily occur to those skilled in the art, it is not desired to limit the invention to the exact construction and operation shown and described, and accordingly, all suitable modifications and equivalents may be resorted to, falling within the scope of the invention.
Number | Date | Country | |
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61735123 | Dec 2012 | US |