Electrical Terminal

Abstract

Disclosed is an electrical terminal whose principal use is in connecting a lead to a terminal area on a printed circuit board. The terminal is formed so that substantially all of the contact area on the terminal is brought into engagement with the terminal area on the printed circuit board. The terminal is also designed so that a spring pressure is applied at both the front and the rear of the terminal's contact area so that this area is constantly biased against the circuit board's terminal area thereby assuring an electrical junction between the two areas capable of carrying a substantial current load.

Description

BACKGROUND OF THE INVENTION

Many electrical terminals are known for connecting a lead to a terminal area on a printed circuit board. With knowledge of the many electrical terminals already available in the prior art for the stated purpose, the terminal of this invention was designed by approaching its construction while considering all of the many aspects of terminal construction. In designing the terminal of this invention, such things as manufacturing feasibility, rapid output on automatic manufacturing machinery, ease of use by assembly personnel and self protecting features for the terminal were taken into consideration from the very outset of the terminal's design. The terminal of this invention is designed so that it takes into account not only electrical characteristics required of the terminal but also manufacturing feasibility as well.

The terminal of this invention is one which is so constructed that it has many advantageous electrical characteristics. The terminal has a contact surface area that will lay in flat contact with an engaged terminal area of a printed circuit board. Also, the terminal is designed so that a spring pressure will be applied between the terminal's contact area and the board's terminal area during their engagement. The terminal is designed so that parallel circuit paths are provided between the lead attached to the terminal and the board's terminal area thus permitting a larger amount of current to be carried by the terminal.

From a mechanical standpoint, the terminal is designed so that an overstressing of the contact element thereof will not be permitted. Also, the terminal is designed to withstand rough handling and it has protective surfaces formed as an integral portion thereof to protect the spring members of the terminal from mishandling. For manufacturing feasibility, the terminal is designed so that large numbers of high quality terminals can be produced rapidly in a progressive stamping operation.

SUMMARY OF THE INVENTION

This invention relates to an electrical terminal and, more particularly, to an electrical terminal which connects a lead to a terminal area of a printed circuit board.

In accordance with the teachings of this invention, an electrical terminal is formed from a single, metal strip. The terminal has a bottom wall which has a front, a back and a pair of side edges. A pair of wall forming elements having side and top wall portions are also provided. The side wall portions of each of the elements extend upwardly from an opposed side edge of the bottom wall and each of the top wall portions of the elements extend inwardly from an opposed edge of an associated one of the side wall portions to form at least half of the entire top wall of the terminal. Each of the top wall portions of the wall forming elements are notched to define an opening in the top wall. A surface of the top wall adjacent the front of the terminal forms an initial top wall surface. A terminal element extends from the front edge of the bottom wall of the terminal and this element has, in order, a first spring member having a radius surface portion and a lead radius portion, a weakened section, a contact surface, a second spring member, and a foot. The radius surface portion of the first spring member of the terminal element extends from the front edge of the bottom wall and curves upwardly and inwardly of the bottom wall to a point engaging the rear edge of the initial top wall surface to store an amount of stress in the terminal element. The lead radius portion of the first spring member extends upwardly from the radius surface portion through and beyond the top wall to a point which is tangent to a horizontal plane, which plane is parallel to the terminal's bottom wall but spaced above its top wall. The weakened section interconnects at the tangent point, the first spring member and the contact surface. The contact surface, which connects with the terminal area of the printed circuit board, is at a slight downward angle to the mentioned horizontal plane. The second spring member of the terminal element extends downwardly from the rear of the contact surface through the opening of the terminal's top wall into the interior of the terminal. The foot terminates the second spring member and the foot contacts the bottom wall of the terminal. A gripper device extends from the back edge of the terminal's bottom wall to secure a lead to the terminal.

In greater detail, the top wall portions of the pair of wall forming elements are notched to define at least a front and a rear opening in the terminal's top wall with an intervening surface therebetween. The lead radius portion of the first spring member extends out of the front opening and the second spring member extends into the second opening. The intervening surface has an upwardly facing projection formed thereon for engaging the contact surface when that surface is pushed downwardly from a normal position more than a desired amount thereby to prevent overstressing of the terminal element. The height of the projection above the intervening surface controls the degree to which the terminal element may be stressed.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of the electrical terminal of this invention.

FIG. 2 is a side elevation view of the terminal of FIG. 1.

FIG. 3 is a front elevation view of the electric terminal of FIG. 1.

FIG. 4 is a plan view of the electrical terminal of FIG. 1.

FIG. 5 is a side elevation view, in cross section, taken along line 5--5 of FIG. 4.

FIG. 6 is a cross section view taken along line 6--6 of FIG. 5.

DESCRIPTION OF THE PREFERRED EMBODIMENT

In the drawings, the electrical terminal of this invention is generally designated by the numeral 10. The terminal has a bottom wall 12 which is in the form of a rectangle having a pair of side edges, a front edge and a back edge. The electrical terminal is formed from a unitary piece of conductive metal. A pair of wall forming elements, generally designated by the numerals 14 and 16, each have side, top, and front wall portions. In the case of the wall forming element 14, the side wall portion thereof is 18, the top wall portion thereof is 20, and the front wall portion thereof is 22. In the case of the wall forming element 16, the side wall portion thereof is 24, the top wall portion thereof is 26, and the front wall portion thereof is 28. Each of the side wall portions 18 and 24 extends upwardly from an opposed side edge of the bottom wall 12. Each of the top wall portions 20 and 26 extend inwardly from an opposed edge of an associated one of the side wall portions to form at least half of the entire top wall of the terminal (best seen in FIG. 1).

The top wall portion 20 is notched to provide openings 30 and 32 therein as is best seen in FIGS. 1 and 4. Similarly, the top wall portion 26 is notched to provide openings 34 and 36 therein. The openings 30 and 34 combine to provide a front opening for the top wall of the terminal while the openings 32 and 36 combine to form a rear opening for the top wall of the terminal.

Projecting portions 38, 40 and 42 are formed on the top wall portion 20 as best seen in FIGS. 1 and 4. Similarly, projecting portions 44, 46 and 48 are formed on the top wall portion 26. The projecting portions 38 and 44 combine to form an initial top wall surface. The projecting portions 40 and 46 combine to form an intervening surface between the openings of the top wall. The projecting portions 42 and 48 combine to form a rear top wall for the terminal.

Each of the front wall portions 22 and 28, respectively of the wall forming elements 14 and 16, extend outwardly from the projecting portions 38 and 44. The front wall portions 22 and 28 are curved downwardly and together they provide a guiding surface which aids in directing the terminal 10 into an opening of a connector block (not shown). The guiding surface also functions to protect the active terminal element of the terminal 10 from damage during terminal insertion. The projecting portion 46 of the top wall portion 26 of the wall forming element 16 has an upstanding projection 50 formed thereon for purposes to be described hereinafter.

A terminal element, generally indicated by the numeral 52, is provided as a principal element of the terminal 10 of this invention. The terminal element 52 is divided into the following principal parts: a first spring member, generally identified by the numeral 53 which includes a radius surface portion 54 and a lead radius portion 56, a weakened section 58, a contact surface 60, a second spring member 62, and a foot 64.

The radius surface portion 54 of the first spring member 53 of the terminal element 52 extends upwardly and inwardly of the bottom wall 12 of the terminal 10. This surface 54 engages the rear edge of the initial top wall surface defined by the projecting portions 38 and 44 of the top wall portions 20 and 26 respectively of the wall forming elements 14 and 16. The engagement of the radius surface portion 54 with this surface serves to pre-stress and store that stress in the terminal element 52.

The lead radius portion 56 of the first spring member 53 extends from the radius surface portion 54 outwardly through the front opening provided in the top surface of the terminal 10. This first spring member 53 serves to provide a spring force on the contact surface 60 when the contact surface is in engagement with a terminal area of a printed circuit board. As is best understood by reference to FIG. 2, the member 53 extends upwardly to a point 66 which is tangent to an imaginary plane 68. The plane 68 is parallel to the bottom wall 12 but spaced upwardly and above the top wall of the terminal.

At the tangent point 66, the weakened section 58, which is weakened by providing a rectangular shaped depression in the underpart of the terminal element 52 at this point, is employed to interconnect the contact surface 60 with the first spring member 53. Placement of the weakened section 58 at this tangent point 66 is critical in that such placement insures that the first spring member 53 and the second spring member 62 will act on the contact surface 60 to force the contact surface into intimate contact with a terminal area of a printed circuit board and provide a flat, uniform junction therebetween. The weakened section, in effect, acts to direct the point of bending of the contact area into engagement with a terminal area of a printed circuit board when the same is deformed thereagainst. When such a contact is made in a flat manner, a parallel circuit path is obtained through the terminal 10. One path is through the first spring member 53 and the contact surface 60 while the other path is through the second spring member 62 and the contact surface.

The contact surface 60 of the terminal element 52, in a normal condition as shown in the drawings, is at a slight downward angle with respect to the imaginary plane 68. The preferred downward angle is about 3.degree.. The downward angle is selected so that the contact area will properly flatten against the contact area of the printed circuit board when it is brought into contact therewith. The flattening of the contact surface comes about because the contact surface 60 is depressed downwardly toward the upstanding projection 50. This downward depression is resisted by the first spring member 53 on one side of the contact surface and by the second spring member 62 and on the other side of the contact surface. The position of the contact surface 60 with respect to the first spring member 53 may change slightly at the weakened section 58 so that the contact surface 60 is deformed into a complete area contact with the terminal area of the printed circuit board. After such a contact has been established, the spring members 53 and 62 serve to apply a continuous spring force on opposite ends of the contact area to assure that this contact area is held in flat, parallel engagement with the printed board terminal area.

The second spring member 62 of the terminal element 52 extends downwardly from its point of engagement with the contact surface 60 through the rear opening in the top wall of the terminal 10. As is best understood by reference to FIGS. 1 and 4, the second spring member 62 tapers inwardly as it progresses downwardly to its terminal point. The reason that the member is tapered is so that it will gve a greater springback than a simple linear member. This is an optimization of the spring member deflection characteristic.

The foot 64 of the terminal element 52 terminats the second spring member 62. The foot 64 is in engagement with the bottom wall 12 of the terminal 10. The foot has an upturned shape so as to guarantee that the second spring member 62 will not dig into the botton wall. The foot 64 allows the second spring member 62 to slide across the bottom surface so that the contact surface 60 may be displaced downwardly as viewed in FIGS. 2 and 5.

An opening 70 is provided in the bottom wall of the terminal 10 as best seen in FIGS. 2 and 5. The purpose of this opening 70 is to provide a space into which a locking finger may be moved to lock the terminal 10 within a connector block (not shown). The locking finger arrangement may be similar to that described in U.S. Pat. No. 3,601,760 issued on Aug. 24, 1971 to T. M. Cairns.

The upstanding projection 50 is formed on the projecting portion 46 of the top wall portion 26 of the wall forming element 16 is designed so that the contact portion 60 of the terminal element 52 will not be overstressed because the terminal element can not be deformed beyond a predetermined limit. In particular, the contact surface 60 may be deformed downwardly from the plane 68 only to the point at which the bottom of the contact surface engages the upstanding projection 50. This limits the total travel of the contact surface and the limit is so designed that the terminal element 52 is not unacceptably overstressed. Upon release of the deforming pressure, the terminal element 52 will substantially return to its normal position.

To the rear of the bottom wall 12 is formed a gripper structure generally designated by the numeral 72. This gripper structure is designed to engage and hold the bare ends of an electrical lead wire (not shown) therewithin. Such a structure is well known in the art and no further description will be included herein.

There has been disclosed herein a preferred embodiment of an electrical terminal in accordance with the teachings of this invention. Many modifications of this disclosed electrical terminal will be apparent to those skilled in the art in view of the detailed teachings of this specification. It is intended that all such modifications which fall within the true spirit and scope of this invention be included within the scope of the appended claims.

Claims

We claim:

1. An electrical terminal formed from a single metal strip which comprises:

a bottom wall having front, back and side edges;

a pair of wall forming elements having side and top wall portions; each of said side wall portions extending upwardly from an opposed side edge of said bottom wall; each of said top wall portions extending inwardly from an opposed edge of an associated one of said side wall portions to form at least half of the entire top wall of the terminal, each of said top wall portions being notched to define an opening over at least a portion of said top wall, each of said top wall portions forming an initial top wall surface adjacent the front of the terminal;

a terminal element extending from said front edge of said bottom wall, said terminal element having, in order, a first spring member having a radius surface portion and a lead radius portion, a weakened section, a contact surface, a second spring member, and a foot; said radius surface portion of said first spring member curving upwardly and inwardly of said front edge of said bottom wall to a point engaging the rear edge of said initial top wall surface defined by said top wall portions thereby to store an amount of stress in said terminal element; said lead radius portion of said first spring member extending upwardly from said radius surface portion through and beyond said opening in said top wall to a point tangent to a horizontal plane, which plane is parallel to said bottom wall but spaced above said top wall; said weakened section at said tangent point interconnecting said first spring member and said contact surface; said contact surface being at a slight downward angle with respect to said horizontal plane; said second spring member extending downwardly through said opening of said top wall into the interior of said terminal; said foot terminating said second spring member and contacting said bottom wall; and

gripper means extending from said back edge of said bottom wall for securing a lead to the terminal.

2. The electrical terminal as defined in claim 1 wherein: said top wall portions of said pair of wall forming elements are notched to define at least a front opening and a rear opening in said top wall with an intervening surface therebetween; said lead radius portion of said first spring member extending out of said front opening and said second spring member extending into said second opening; said intervening surface providing a stop surface which is engaged by the underside of said contact surface to prevent overstressing of said terminal element.

3. The electrical terminal as defined in claim 2 wherein: an upwardly facing projection is formed on said intervening surface, said projection engaging the underside of said contact surface when said surface is deformed a determined amount to prevent overstressing of said terminal element, the height of said projection above said intervening surface controlling the degree to which said terminal element may be stressed.

4. The electrical terminal as defined in claim 1 wherein: said slight downward angle of said contact surface with respect to said horizontal plane is no more than 3.degree..

5. The electrical terminal as defined in claim 1 further including: front wall portions formed on said pair of wall forming elements, each of said front wall portions extending forwardly from an associated one of said top wall portions defining said initial top wall surface, said front wall portions forming a guiding surface for terminal insertion.

6. The electrical terminal as defined in claim 1 wherein: said weakened section is formed by deforming a portion of the metal of said terminal element to a thickness less than the thickness of said metal.

7. The electrical terminal as defined in claim 1 wherein: said second spring member tapers inwardly from said contact surface to said foot.

8. An electrical terminal formed from a single, metal strip which comprises:

a bottom wall having front, back and side edges;

a pair of wall forming elements having side, top and front wall portions, each of said side wall portions extending upwardly from an opposed side edge of said bottom wall; each of said top wall portions extending inwardly from an opposed edge of an associated one of said side side wall portions to form at least half of the entire top wall of the terminal, each of said top wall portions having notches therein providing openings in both the front and the rear of said entire top wall, the surfaces of said top wall portions forming both an intervening surface between said openings and an initial top wall surface adjacent the front of the terminal; each of said front wall portions extending forwardly and downwardly from a respective one of said top wall portions which forms said initial said top wall surface to provide a terminal nose surface;

a terminal element extending from said front edge of said bottom wall, said terminal element having, in order, a first spring member with a radius surface portion and a lead radius portion, a weakened section, a contact surface, a second spring member, and a foot; said radius surface portion of said first spring member curving upwardly and inwardly of said front edge of said bottom wall to a point engaging the rear edge of said initial top wall surface; said lead radius portion of first spring member extending upwardly from said radius surface portion through and beyond said front opening in said top wall to a point tangent to a horizontal plane, which plane is parallel to said bottom wall but spaced above said top wall; said weakened section at said tangent point interconnecting said first spring member and said contact surface; said contact surface being at a slight downward angle with respect to said horizontal plane, said contact surface overlying bu t spaced above said intervening surface of said top wall; said second spring member extending downwardly from said contact surface through said rear opening of said top wall into the interior of the terminal; said foot terminating said second spring member and contacting said bottom wall; and

gripper means extending from said back edge of said bottom wall for securing a lead to the terminal.

9. The electrical terminal as defined in claim 8 wherein: an upwardly facing projection is formed on said intervening surface, said projection engaging the underside of said contact surface when said surface is deformed a determined amount to prevent overstressing of said terminal element, the height of said projection above said intervening surface controlling the degree to which said terminal element may be stressed.

10. The electrical terminal as defined in claim 8 wherein: said slight downward angle of said contact surface with respect to said horizontal plane is no more than 3.degree..

11. The electrical terminal as defined in claim 8 wherein: said weakened section is formed by deforming a portion of the metal of said terminal element to a thickness less than the thickness of said metal strip.

12. The electrical terminal as defined in claim 8 wherein: said second spring member tapers inwardly from said contact surface to said foot.