US 3215975 A
Description (OCR text may contain errors)
Nov. 2, 1965 R. J. KlNKAlD CONNECTOR BLOCK ASSEMBLY 2 Sheets-Sheet 1.
Filed Nov. 27, 1961 INVENTOR. ROBERT 3'. \MNKPuu Nov. 2, 1965 R. J. KINKAID CONNECTOR BLOCK ASSEMBLY 2 Sheets-Sheet 2 Filed Nov. 27, 1961 ROBERT J. \MNKMD United States Patent 3,215,975 CGNNECTOR BLOCK ASSEMBLY Robert .F. Kinkaid, New Cumberland, Pa., assignor to AMP Incorporated, Harrisburg, Pa. Filed Nov. 27, 1961, Ser. No. 157,037 3 Claims. (Cl. 339-256) This invention relates, in general, to a connector block assembly for wiring electrical systems, particularly for a system including banks or arrays of printed circuit boards or cards. This application is a continuation-in-part of my prior application, Serial No. 75,955, filed December 15, 1960 now abandoned.
A variety of connectors have been proposed for incorporating banks of printed circuit cards in a system, but the lack of versatility, reliability, ruggedness and economy, in more or less degree, is a common failing.
An important feature of the invention, therefore, is the provision of a rugged and reliable connector assembly easily adaptable to a variety of functions and forms in the wiring of printed circuit card banks in electrical systems. To this end, as an objective the connector assembly of this invention includes a multi-contact plug block and a mating socket block, wherein the plug block may be formed so as to connect a printed circuit card individually into one of an array of socket blocks, or additionally may provide connections for two or more socket blocks to a single printed circuit card, or merely to provide feedthrough connections for two or more socket blocks.
Another feature of the invention concerns the character of the contacts in the plug and socket blocks which are simple and rugged, yet are producible with a wide range of manufacturing tolerances. Another feature lies in the preservation of long life of the contacts by providing a slide-fit engagement which is highly wear-resistant. Closely allied with this feature lies the reliability of contact engagement by multiplicity of contact points between the contacts of the plug and socket blocks, and between the plug contacts and the printed circuit cards.
An additional feature resides in the provision of a commercially feasible organization of parts which overcomes certain disadvantages inherent in the structures of the prior art, which features will become apparent to those skilled in the art upon reading the following detailed description when taken in conjunction with the drawings in which:
FIGURE 1 is a perspective view of an embodiment of a connector block assembly according to the present invention;
FIGURE 2 is an enlarged side view, in section, of the connector assembly of FIGURE 1, but with the connector blocks engaged;
FIGURE 3 is a fragmentary sectional view taken along lines 33 of FIGURE 2;
FIGURE 4 is a fragmentary sectional view, further enlarged, taken along lines 44 of FIGURE 2;
FIGURE 5 is an enlarged perspective view of a contact for insertion in the socket block of the assembly;
FIGURE 6 is a sectional perspective view illustrating a modified form of a connector block assembly of the invention;
FIGURE 7 is a sectional perspective view illustrating another modified form of the plug block; and
FIGURE 8 is a sectional perspective view of another embodiment of a plug block of the invention.
With reference to the embodiment of the invention, as shown in FIGURES 1-5, the connector block assembly includes a plug block 2 mounted on a printed circuit card 4 for cooperation with a socket block 6 to complete circuit connections from the printed circuit lines 8 and the electrical components (not shown) on card 4 to lead 3,215,975 Patented Nov. 2, 1965 wires 10 associated with socket block 6 which lead to other apparatus of the electrical system involved.
The body of plug block 2 is of suitable insulating material and carries a row of plug contacts 12 which preferably are sheet-metal stampings from brass coated with a gold plating, especially when used for dry circuit connections. Conveniently, plug contacts 12 are insert-molded in plug block 2, and to this end the main body portion 14 has a central aperture 16 through which insulation of block 2 may extend for firmly anchoring the contacts. Each plug contact has a pair of tangs 18 projecting from the bottom surface of plug block 2 and received in a pair of apertures 20 in printed circuit card 4 for solder connection 22 in the usual manner to a printed circuit line 8 that passes by the apertures. Two such tangs are preferred to protect against faulty solder connections by multiplicity. Each plug contact 12 further has a plug part projecting from the forward face of plug block 2, advantageously in the form of a generally rectangular blade 24 having smoothly rounded corners on one side to provide a pair of longitudinally extending contact surfaces 26 as best shown in FIGURE 4. Preferably, the rounded corners are achieved by coining the edges of a flat sheet metal blank, thus to maintain close tolerances. In cross-section, contact surfaces 26 are arcuate on a radius of curvature which breaks the corners of the blade to the extent of about one-half the stock thickness. The side of the blades containing the contact surfaces 26, for convenience in assembly, all face in the same direction.
Socket block 6, also preferably molded from a suitable insulating plastic material, is generally rectangular and has a row of through passageways 28 extending between its front and back faces 30 and 32 respectively, thus to admit in their front end the row of plug blades 24 for cooperative engagement with a corresponding set of socket contacts 34 received into the back face of the passageways and supported in the socket block. The socket contacts also are of a form suitable for fabrication by sheet metal stamping techniques, preferably from a metal having spring qualities; e.g., Phosphor bronze with a highly conductive and corrosive-resistant coating such as a gold plating, and include an alongated blade-receiving socket section defined by a base 36 having a pair of opposed side flanges 38 bent back upon the base toward one another with their end edges 40 spaced less than the width of blades 24. Side flanges 33 additionally are curved, preferably by a coining operation to achieve close tolerances, on a radius of curvature slightly larger than the radius of curvature of plug contact surfaces 26, thus to provide mating contact surfaces 42 on their inside surfaces, the tangent at end edges 4t) to this curvature projecting at a diverging angle relative to socket base 36. A radius of curvature for side flanges 38 of approximately 1 /2 times the radius of curvature of plug surfaces 26 has been found to be mechanically optimum.
As thus constructed, when a blade 24 is telescoped with a socket contact 34 and relatively pressed against side finages 38, plug contact surfaces 26 are accommodated within the curvature of socket contact surfaces 42, effecting a predictable and constant quality of electrical engagement in their areas of meeting regardless of a wide range of configurational departures caused; for example, by accidental deformation or design tolerances. A spring prong 44 struck out of base 36 and extending inwardly and forwardly in socket contact 34 supplies the spring pressure for biasing or pressing blade 24 against flanges 38. Further, prong 44 is generally arcuate transversely of its axis with its free end normally positioned below the inside surface of base 36 so as not to interfere with the plug blade on insertion.
Socket contacts 34 advantageously are rather loosely mounted in socket block 6 in a snap-in relation so that they can adjust individually to the entrance angle of the rig-idly mounted plug blades 24 into passageways 28. In this regard, a spring detent 46 struck out of base 36 and extending inwardly and rearwardly in socket contact 34 is arranged to engage behind a stop shoulder 47 extending inwardly from a sidewall of passageway 28 as the forward end of the socket contact approaches lips 48 at the forward end of the passageway upon insertion of the socket contact from the back face 32 of the socket block. Stop shoulder 47 is centrally arranged on the sidewall of the passageway so that on proper insertion of a socket contact 34, it will be passed in the space between end edges 40 of side flanges 38. If an attempt is made to insert the socket contact upside down, however, base 36 will be obstructed by stop shoulder 47, thus to assure that all the socket contacts will be properly inserted to face in the same direction and in proper orientation relative to blade contacts 12.
At the rearward end of each socket contact, suitable means are provided for connection with lead wires 10. Typically, such means, as shown in FIGURE 5, may comprise two pairs of ears 50 and 52 crimped about the stripped metallic core 54 and the insulation 56, respectively, of the lead Wire in a manner well-known in the art.
To interfit the blocks simply and accurately, alignment and guide means are provided, preferably of a form adding no parts or manufacturing complexity. Thus, socket block 6 is molded with a pair of integral guide lugs 58 projecting forwardly from front face 30 along which extends a slot 60. Lugs 58 are spaced to guide an extended portion 62 of printed circuit card 4 into slot 60 as blades 12 are thereby aligned with and enter passageways 28.
A pair of side lugs 64 for rack-mounting socket block 6 may be provided, if desired.
As thus constructed and arranged, the parts are seen to be of simple and rugged construction, yet highly reliable and effective in performance. For example, the spring portions, viz., prong 44 and detent 46, are wholly protected by being enclosed within the channel configuration of socket contact 34. Further, it is contemplated that in normal use the solid crimp section of the socket contact, including cars 50 and 52, will have slightly larger cross-sectional dimensions than the contact section 1ncluding flanges 38, thereby tending first to absorb any external shocks.
Moreover, even should flanges 38 become distorted as by being bent more or less closed, the quality of electrical contact will not suffer so long as blade 24 is capable of entering the socket contact channel, since the accommodation of curved contact surfaces 26 to contact surfaces 42 is essentially independent of the angle of flanges 38 or the relative thickness of the blade. Forceful insertion of a blade 24 is also effective to reform the flanges to operative condition. It is to be understood, however, that in normal use the main body of socket contact 34, including side flanges 38 and base 36, is intended to be a rigid structure which does not bend or deflect to any significant extent on insertion of blade 24. That is to say, the character and control of the contact pressure between the mating parts is preferably determined primarily by the character and design of spring 44. More constant and predictable quality of electrical contact can be thus achieved.
In relation to the character of the electrical contact and contact pressure between surfaces 26 and 42, it will be apparent that under the force exerted by spring 44, blade 24 tends to wedge and bend side flanges 38 apart. The magnitude of the wedging force, for a given spring pressure, will depend upon the angle between the line tangent to the contact point of surfaces 26 and 42, and the line along which the force of spring 44 is applied, i.e., a line perpendicular to the base of blade 24. More specifically stated, the normal force, F,,, at the point of contact is equal to the applied force, F delivered by spring 44, divided by sin 0. Where angle 0 is low, i.e., the contact point is low along the side of blade 24, the normal force can become quite high, disadvantageously tending to bend flanges 38 and increasing the force require-d to insert the blade and the wear on the parts during insertion, perhaps to the point of destruction of any gold plating. Accordingly, it is important that angle 0 have a high value; in practice 68 have been found to be optimum, although angles within the range 63 to 73 are acceptable.
It is also important to note that the contact assembly is polarized; that is, blade 24 cannot be inserted into the channel of socket contact 34 upside down because the unbroken or square side corners of the blade would interfere with flanges 38. In other words, side flanges 38 are turned inwardly sufliciently far that, relative to the width and thickness of rectangular blade 24, the channel of the socket contact will not admit the blade but for the breaking of side corners 26.
Turning now to FIGURE 6, there is illustrated a modified form of the connector block assembly according to the invention, wherein provision is made for coupling multiple socket block-s to a plug block arranged to carry a single printed card, as is occasionally required in wiring or testing more complex electrical systems. As shown, the plug contacts 66 of plug block 68 each include a bus bar 70 having a number of lateral strips 72 on opposite sides terminating in contact blades 74a, 74b and 74c projecting from opposite faces of the block. Tangs 76 for eletcrically and mechanically mounting a printed circuit card extend laterally from one such strip 72 through the top side of the block. Similar blades, 74a, 74b and 74c, staggered to conserve center-to-center spacing of the various plug contacts 66, are arranged in rows for cooperation with socket blocks 78a, 78b and 78c respectively, but it will be understood that bus bar 70 may be extended to provide as many rows of contact blades on only one or both faces of the plug block as required by the conditions of a particular use. A guide pin 80 on the plug 'block, there being preferably one such on each end of each row of contact blades in cooperation with associated bores 82, serves to align and guide the socket blocks into proper interfitting relation on the plug block.
Alternatively, as shown in FIGURE 7, the plug block may serve merely as a feed-through connector for coupling the row of contacts of one socket block to the contacts of one or more other socket blocks as desired, omitting the tangs for coupling to a printed circuit card. In this form, the multiple strips 84 extending from bus bar 86 simply terminate in contact blades 88a, 88b 88c and 88d in multiple rows on opposite faces of the plug block 90.
The pair of tangs depending from each contact blade advantageously affords multiplicity of contact with a single circuit strip on the printed circuit card. Occasionally, however, it may be necessary to sacrifice this advantage in favor of increasing the number of circuit lines to the card. In this event, as shown in FIGURE 8, in each vertical station of the plug contacts, strips 92a and 92b are separated to terminate in electrically disconnected tangs 94a and 94b projecting from the bottom side of plug block 96 and contact blades 98a and 98b on the front face of the block, respectively. Tang 94a may then be solder-connected to a printed circuit line 100a on the upper side of circuit card 102, for example, while tang 94b connects with another circuit line 10Gb on the lower side of circuit card 102.
In this specification and accompanying drawings, I have shown and described a preferred embodiment of my invention and suggested various modifications; but it is to be understood that these are not intended to be exhaustive nor limiting of the invention but, on the contrary, are given for purposes of illustration in order that others skilled in the art may fully understand the invention and the principles, and the manner of applying it in practical use so that they may modify and adapt it in various forms, each as may best be suited to the conditions of a particular use.
1. A slide-fit electrical contact assembly comprising a rigid blade and a socket adapted to interfit telescopically, said blade being generally rectangular in cross-section With flat top and bottom surfaces and having rounded corners on one side, said socket including a base having a pair of spaced, opposed side flanges extending toward each other generally at an acute angle away from said base, said flanges being rounded over substantially their full extent on a radius of curvature no less than the curvature of said rounded corners, and spring means arranged to press the blade against said flanges with the rounded corners engaging the curved portions of said side flanges, at points within the engage-ment portions intermediate the extent of said side flanges, said flanges being inflexible relative to said spring means, the width of said blade adjacent said bottom surface being less than the width of the base of said socket to avoid contact between the socket and the sides of said blade, said width being greater than the maximum spacing between the engagement portions of said side flanges.
2. A contact assembly according to claim 1 wherein the radius of curvature of said flanges being approximately 1% times that of said rounded corners.
3. A contact assembly according to claim 1 wherein said angle is approximately 68.
References Cited by the Examiner UNITED STATES PATENTS 1,769,325 7/30 Warner 339-278 2,233,067 2/41 Alden 339- 2,243,741 5/41 Rowe.
2,427,182 9/47 Bergan 339-244 2,551,423 5/51 De Vito 339-258 X 2,724,811 11/55 Poupitch 339-258 X 2,728,061 12/55 Bliss et al 339-196 2,740,944 4/56 Harrison et al 339-192 2,768,361 10/56 Aquillon et al 339-211 2,791,755 5/57 Hammell 339-258 2,946,976 7/60 Blain 339-17 2,965,872 12/60 Linn 339-159 2,984,814 5/61 Scott 339-17 X 3,102,768 9/ 63 Schwamb 339-262 X JOSEPH D. SEERS, Primary Examiner.