US3850498A

US3850498A - Filter assembly for printed circuit board connectors

Info

Publication number: US3850498A
Application number: US00315051A
Authority: US
Inventors: F Schor
Original assignee: AMP Inc
Current assignee: TE Connectivity Corp
Priority date: 1971-05-27
Filing date: 1972-12-14
Publication date: 1974-11-26
Anticipated expiration: 1991-11-26
Also published as: US3720903A

Abstract

A filter assembly for a printed circuit board connector having spring contacts with crimp barrels for connecting flexible leads. The assembly includes a ground strap having a first curved surface at one side resiliently engaging the crimp barrel of one spring contact connected to a grounded flexible lead. A second curved surface at the other side of the ground strap resiliently engages the exterior (i.e., the ground side) of a cylindrical filter. A connecting pin extending through the filter is engaged by a crimp barrel of an adjacent ungrounded spring contact. By recessing the second curved surface with respect to the first, the second curved surface will not contact the ungrounded spring contact. A notch is provided in the intermediate portion of the strap to receive a wall of the connector housing separating the spring contacts. The filter need not in every instance be connected to a grounded circuit.

Description

Unite ttes Ptent 1 in] 3,850,98 Sehor Nov. 26, 1974 FILTER ASSEMBLY FOR PRINTED CIRCUIT BOARD CONNECTORS Ferdinand William Schor, Altedena, Calif.

Assignee: AMP incorporated, Harrisburg, Pa. Filed: Dec. 14, 1972 Appl. No.: 315,051

Related U.S. Application Data I Division of Ser. No. 147,570, May 27, 1971, Pat. No. 3,720,903.

Inventor:

References Cited UNITED STATES PATENTS Deakin 339/147 P Fort 33 /147 R Primary Examiner-Paul R. Gilliam Assistant ExaminerRobert A. l-lafer Attorney, Agent, or Firm-Gerald K. Kita [57] ABSTRACT A filter assembly for a printed circuit board connector having spring contacts with crimp barrels for connecting flexible leads. The assembly includes a ground strap having a first curved surface at one side resiliently engaging the crimp barrel of one spring contact connected to a grounded flexible lead. A second curved surface at the other side of the ground strap resiliently engages the exterior (i.e., the ground side) of a cylindrical filter. A connecting pin extending through the filter is engaged by a crimp barrel of an adjacent ungrounded spring contact. By recessing the second curved surface with respect to the first, the second curved surface will not contact the ungrounded spring contact. A notch is provided in the intermediate portion of the strap to receive a wall of the connector housing separating the spring contacts. The filter need not in every instance be connected to a grounded circuit.

6 Claims, 6 Drawing Figures SHEET 2 OF 2 PATENTH NOV 2 6 I974 CROSS REFERENCE TO RELATED APPLICATION This is a division of my application Ser. No. 147,570

filed May 27, 1971, now US. Pat. No. 3,720,903.

BACKGROUND OF THE INVENTION This invention relates to electrical connectors wherein one or more RF filter assemblies comprising capacitive, inductive and/or lossy circuit elements are electrically connected to the contact terminals of the connector so as to attenuate undesired RF signals which would otherwise pass through the connector. The present invention relates more particularly to RF filters of the type disclosed in US. Pat. No. 3,743,978, and the use of such filters in electrical connectors wherein one or more spring contact terminals are assembled into one connector member and mating contacts are mounted on a PC (printed circuit) board member to provide one or more electrical circuits upon engagement by the spring contacts.

'A PC board connector with flexible leads usually consists of an insulating housing having a double row of spring contact terminals designed to make electrical connection to a row of metallic tabs on one or both surfaces of a PC board. The PC board contains a portion of the electrical components of the equipment which are connected together, usually by printed circuitry appearing on one or both sides of the PC board. Connection to the remaining circuitry of the equipment is then made through flexible leads attached to the PC board connector. Thus, the PC board can be easily removed for changes or repair by simply pulling the PC connector off and detaching the PC board from its mounting.

Where the PC board contains sources of high frequency interference such as oscillators, SCR rectifiers, pulse circuits, high voltage diodes, etc., it is desirable to keep this interference from propagating through the connector terminals and lead wires to other parts of the equipment. Such high frequency interference appearing in other parts of the equipment containing sensitive circuits could result in the malfunctioning of the entire system.

In order to overcome the undesired effects produced by high frequency interference associated with PC boards, the prior art has provided several layers of copper separated by an insulating dielectric to provide large capacities between the printed circuit wiring and another layer of copper which forms a grounded plane. Such a combination provides an RF filter for the PC board. However, this approach is expensive and does present the risk of a short circuit between the printed circuit wiring and the grounded conductive plane.

US. Pat. No. 3,275,954 to Coda et al and US. Pat. No. 3,462,715 to Schor disclose filters for use in connector assemblies receiving connector pins. However, such connector assemblies are not adapted to receive printed circuit boards.

SUMMARY OF THE INVENTION It is a general object of this invention to provide a means for preventing undesirable coupling of high frequency interference to or from a PC board.

It is a further object of this invention to provide such a means at minimal expense.

It is also an object of this invention to provide such a means and eliminate the possibility of an electrical short circuit in the printed circuit wiring of the PC boards.

It is a more specific object of this invention to provide a PC board connector with self-contained low pass filters for reduced coupling of high frequency interference to the PC boards.

It is a further specific object of this invention to prevent such interference from being transmitted through flexible leads connected to spring contacts within the PC board connector. 7

It is another specific object to provide a low pass filter assembly requiring no tooling changes in a conventional PC connector housing.

It is a further specific object to provide such a filter assembly requiring no soldering.

It is a still further specific object to provide filtering between any pair of PC board connector terminals with or without connection to the ground plane on the PC board.

It is also a specific object to provide easy insertion and removal of the filter so that a filter may be inserted anytime it is found necessary or removed for replacement if ever required.

In accordance with these and other objects, the invention may be embodied in a filter assembly comprising a low pass filter associated with a spring contact forming a terminal in a printed circuit board connector. A ground strap connects the exterior of the filter to another spring contact forrning an adjacent terminal in the PC board connector which may be maintained at ground potential. The ground strap may comprise a first curved surface for resiliently engaging the crimp barrel of the grounded spring contact and a second curved surface for resiliently engaging the exterior of the filter. An intermediate portion is joined with and extends between the curved surfaces. The filter may be substantially cylindrical having a connecting pin threading through the filter and contacting its inside surface. This pin is engaged by the crimp barrel of the ungrounded spring contact at one end and an external connecting lead at the other end.

In accordance with one important aspect of the in vention, the curved surface resiliently engaging the exterior of the filter is recessed with respect to the curved surface engaging the grounded spring contact so as to preclude the possibility of a short circuit between the exterior of the filter (ground side) and the ungrounded spring contact.

In accordance with another important aspect of the invention, the intermediate portion of the ground strap is notched so as to receive a spring contact separator wall of the PC board connector housing and provide additional mechanical support.

BRIEF DESCRIPTION OF TI-E DRAWINGS FIG. 1 is a perspective view of a PC board inserted into a conventional PC board connector;

FIG. 2 is a sectional view of the conventional PC board connector of FIG. 1;

FIG. 3 is a partial view of the flexible lead side of the conventional PC board connector of FIG. I;

FIG. 4 is a perspective view of a spring contact for a conventional PC board connector with a low pass filter attached in accordance with this invention;

F IG. 5 is a perspective view of a ground strap for use in providing a ground path for filter of FIG. 4 in accordance with this invention; and

FIG. 6 is a sectional view of a conventional PC board connector of FIG. 1 in combination with a filter assembly embodying the invention.

DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT FIG. 1 shows an assembly of a conventional PC board 1 with components 2 after insertion into a conventional PC board connector 3. Note the contact tabs 4 which make contact with spring contacts 5 shown in FIG. 2 once the board 1 is inserted into the connector 3. The spring contacts 5 exert pressure on the tabs 4 so as to provide good electrical contact with the tabs 4 as well as retaining the board 1 in the connector 3.

As best shown in FIGS. 2 and 3, the contact housing 7 including a center separator wall 8 serves to maintain the contacts 5 in place within the housing cavity. External connection through flexible leads 21 may then be made at the terminals 9 of the spring contacts 5 either by soldering or crimping.

In accordance with this invention, the terminal 9 of a conventional spring contact 6 is modified to accommodate a low pass filter. Such a modified contact 6, in combination with a low pass filter 11 is shown in FIG. 4. A pin 12 extending through the filter 11 is inserted into the contact crimp barrel with the barrel then crimped in place with a tool. Note the foreshortening of the terminal behind the crimp barrel 10 as compared with the terminal 9 of the conventional spring contact shown in FIG. 2. The pin 12 also carries the barrel type contact spring (25) for contact at the inside of the surface of the filter 11 such as that shown in US. Pat. No. 3,181,044 to Duncan. A flexible lead wire connection is provided at the other end of the pin 12. The connection is made by means of a fastener comprising a crimp barrel 13 which is crimped onto the pin 12 and a tenninal including crimp barrels 14 and 15 which are crimped onto the lead conductor and insulation respectively thus connecting flexible lead 16 to the filter assembly. A soldered connection may also be used.

In further accordance with this invention, a ground strap 17 is provided for providing a conductive path between the exterior of the filter 1 1 and a grounded, adjacent contact terminal. As shown in FIG. 5, the ground strap 17 comprises two

curved surfaces

19 and 20, partially closed on themselves with one on each side of the strap. These

curved surfaces

19 and 20 which are substantially cylindrical are joined by a substantially planar intermediate portion 18. In order to permit the use of the ground strap in a conventional printed circuit board connector 3, the intermediate portion 18 includes a notch at one end of the strap 17. As shown in FIG. 6, the notch 18a engages the separator 8. Note that the strap 17 is recessed on the end at one side of the notch 18a to prevent the curved surface 19, which substantially encircles the outer surface of the filter 11, from short circuiting to the spring contact 6. Note that the curved surface 20 extends out beyond the curved surface 19 to engage the crimp barrel 22 which holds the ground lead 21 to the conventional connector spring contact 5. The strap 17 is made of a suitable conductive material for resiliently engaging the crimp barrel 22 and the filter 11. Beryllium copper suitably plated has been found to be particularly good for this purpose.

It may be seen by reference to FIG. 5, that a conventional printed circuit board connector 3 may be provided with a filter assembly. Not only is the filter assembly adapted for use with a conventional printed circuit board connector, but the filter assembly is actually strengthened by the conventional printed circuit board connector. In this connection, the contact separator 8 which is received in the notch 18a actually reinforces the filter assembly. Furthermore, the filter assembly may be easily applied to the printed circuit board connector 3. First, the ground strap is snapped over the filter 11 and the crimp barrel 22 after the

lead

16 and 21 are attached to the

spring contacts

5 and 6. Then the entire filter assembly is inserted into the housing cavities until the retention springs 24- of the

spring contacts

5 and 6 engage the notches 24a in the respective housing cavities. The filter assembly may also be easily removed by inserting a removal tool into the contact side to release the retention springs 24 while simultaneously pushing on

springs

5 and 6 from the same side. A slight pull on

lead wires

16 and 21 then separates the spring contacts from the housing 7.

Although a particular connector 3 and

particular spring contacts

5 and 6 have been disclosed, it will be understood that other conventional connectors may be utilized in combination with appropriately modified filter assemblies constructed in accordance with this invention.

I claim:

1. An electrical connector assembly comprising:

a first spring contact having a terminal adapted to be connected to a flexible lead;

a filter element having a pin extending from at least one end thereof;

a second spring contact having a terminal connected to said pin, said terminal of said second spring contact being shorter than said terminal of said first spring contact; and

an electrically conductive strap comprising:

a first curved surface at one side of the strap at least partially closed on itself;

a second curved surface at the other side of the strap at least partially closed on itself, said second surface being recessed with respect to said first surface at one end of said strap;

an intermediate portion joined with and extending between said first curved surface and said second curved surface;

said first curved surface of said strap resiliently engaging the exterior of said terminal of said first spring contact and said second curved surface of said strap resiliently engaging the exterior of said filter without contacting said shorter terminal of said second spring contact.

2. The electrical connector assembly of claim 1 further comprising:

a printed circuit board connector housing having a first opening receiving said first spring contact, a second adjacent opening receiving said second spring contact, and a wall separating said openings; and

said intermediate portion of said strap including a notch engaging said wall.

3. The electrical connector assembly of claim 2 wherein said first curved surface and said second curved surface are substantially cylindrical and said intermediate portion is substantially planar.

4. The electrical connector assembly of claim 2 wherein said terminal of said second spring contact comprises a crimp barrel engaging said pin.

5. The filter assembly of claim 1 wherein said pin is a part of said second spring contact and formed from the same material. 4

6. The connector assembly for engaging edge pads of a conventional printed circuit board, said connector comprising:

a housing having an elongated circuit board receiving nected to a flexible lead.

Claims

1. An electrical connector assembly comprising: a first spring contact having a terminal adapted to be connected to a flexible lead; a filter element having a pin extending from at least one end thereof; a second spring contact having a terminal connected to said pin, said terminal of said second spring contact being shorter than said terminal of said first spring contact; and an electrically conductive strap comprising: a first curved surface at one side of the strap at least partially closed on itself; a second curved surface at the other side of the strap at least partially closed on itself, said second surface being recessed with respect to said first surface at one end of said strap; an intermediate portion joined with and extending between said first curved surface and said second curved surface; said first curved surface of said strap resiliently engaging the exterior of said terminal of said first spring contact and said second curved surface of said strap resiliently engaging the exterior of said filter without contacting said shorter terminal of said second spring contact.

2. The electrical connector assembly of claim 1 further comprising: a printed circuit board connector housing having a first opening receiving said first spring contact, a second adjacent opening receiving said second spring contact, and a wall separating said openings; and said intermediate portion of said strap including a notch engaging said wall.

5. The filter assembly of claim 1 wherein said pin is a part of said second spring contact and formed from the same material.

6. The connector assembly for engaging edge pads of a conventional printed circuit board, said connector comprising: a housing having an elongated circuit board receiving aperture along one side thereof and at least one contact receiving slot intersecting said aperture, at least one spring contact, each said spring contact including a crimp barrel and a resilient portion adapted to be received in a slot in said housing; at least one filter including a connecting pin extending from both ends thereof, one end being engaged by said spring contact crimp barrel; and at least one contact having a crimp barrel engaging the other end of said connecting pin and having a terminal means adapted to be electrically connected to a flexible lead.