US 2972728 A
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Unite States Patent ELECTRICAL PLUG HAVING SELF-ALIGNING TERMINAL PINS Fred H. Cole, 1028 S. Sierra Bonita, Los Angeles 19, Calif.
Filed June 9, 1958, Ser. No. 740,749
2 Claims. (Cl. 339-64) This invention relates to electrical plugs, and more particularly to electrical plugs having self-aligning resilient terminal pins.
Conventional type electrical connectors generally comprise a plug having a plurality of elongated, rigid terminal pins, either mounted in rigid relation to the plug or floatingly mounted therein on a fixed pivot connection thereto, and a receptacle provided with a corresponding number of elongated spring contacts, either mounted in fixed relation to the plug or floating therein about a fixed pivot point. These connectors have several inherent disadvantages which the present invention overcomes. If one or more of the terminal pins are misaligned with the receptacle contacts, then the misaligned terminal pins will enter into the spring contacts at an angle thereto (provided that they can enter at all), and the resultant heel and toe action of the terminal pin in the receptacle contacts will spread the spring contacts far beyond the normal expansion thereof. As a result, the closing forces to mate the plug and contact will be greatly increased, and the life of the parts will be correspondingly decreased. In addition, the electrical contact area will be decreased and will limit the current-carrying capacity of the connector.
The same disadvantages will occur when one or more of the terminal pins become bent, through normal usage or abuse.
To overcome these disadvantages, applicant has devised a plug provided with a plurality of laterally resilient terminal pins provided with enlarged spherical heads thereon. Thus, if a terminal pin is misaligned with its receptacle contact, the pin will flex so that the head will enter the receptacle contact. The shape of the spherical head insures that no heel and toe action occurs so that the receptacle contacts are spread an amount equal to that if the pin had been aligned therewith. In addition, the spherical head is provided with a conical tip to, aid the insertion of the terminal pin head into the receptacle contacts. When the plug is removed from the receptacle, the misaligned terminal pin or pins will return to their unstressed straight position due to the resiliency thereof. In addition, the resiliency of the terminal pins overcomes accidental bending thereof due to normal usage or abuse.
It is the principal object of this invention to provide an electrical plug having a plurality of terminal pins having laterally resilient shank portions thereof projecting outwardly from the body.
Another object is to provide the above terminal pin shanks with an enlarged spherical head to provide a constant contact area with a receptacle contact, whether alignment or misalignment exists between the terminal pin and the receptacle contact, and a conical tip on the spherical head to facilitate insertion of the terminal pin into the receptacle contact.
A further object of the invention is to provide a plug as set forth in the preceding objects, in which the resilient terminal pin shank has a steel core and an outer copper layer bonded thereto,
2,972,728 Patented Feb. 21, 1961 Other objects and advantages will become apparent in the course of the following detailed description.
In the drawings, forming a part of this application, and in which like parts are identified by like reference num erals throughout the same,
Fig. l is an enlarged sectional view of a plug mated to a receptacle, the plug being constructed in accordance with the invention, and with three sets of mating contacts being shown.
Figs 2 and 3 are diagrammatic views of the mating contacts of the plug and receptacle of Fig. 1, illustrating the relative positions of the contacts when in and out of alignment relative to each other.
Referring now to the drawings, the plug body 10 comprises a base plate 11 and cover plate 12, both formed from a rigid, electrically non-conductive material such as phenolic plastic or the like. The cover plate is formed with a plurality of holes therethrough to receive the electrically conductive terminal pins 13 relatively snugly therein, the pins extending into the coaxially aligned holes 14 in the base plate 11. 'As is evident from Fig. 1, the terminal pins are held captive within the plug body by the engagement of either end of the radially enlarged portion 16 of pin 13 with the shoulder 17 of base plate 11 and the surface of cover plate 12. When assembled, as shown, the base and cover plates are firmly secured to one another by any suitable means (not shown).
The ends of the terminal pins 13 projecting outwardly from the cover plate 12 are internally recessed at 18 in a conventional manner to receive the conductor Wires 19 therein, which are then soldered to the terminal pins. As is obvious, any other form of connecting the conductor wires 19 to the terminal pins 13 may be employed, if desired.
Each terminal pin has an elongated shank portion 20 projecting outwardly from the plug body. The shank 20, illustrated in section in Fig. 1, is formed of copperweld wire and has a steel core 21 and an outer copper layer bonded thereto. Preferably, the copperweld wire is formed with a copper to steel ratio of 40-60. By the use of this material, the shank obtains the advantages of the high elastic resiliency of the steel core and the high electrical conductivity of the outer copper layer. Although the shank 20 is shown as being press fitted into the radially enlarged portion 16 of the terminal pin, it is to be realized that any other manner of rigidly connecting the shank thereto may be employed, if desired.
The outer end of shank 20 has formed thereon a spheriooconical head 23, that is a spherical head having a conical tip thereon, with the apex of the head in alignment with the longitudinal axis of the shank. The spherical diameter of the head is substantially greater than the diameter of the shank. Illustrative only of the dimensions that have been found to be desirable in one embodiment of the invention now in manufacture, the spherical diameter of the head is .040 inch, the shank diameter is .025 inch, and the apex angle of the head is 60.
The receptacle 30, like the plug, comprises a base plate 31 and a cover plate 32, both plates being formed from a rigid, electrically non-conductive material. The sleeve contacts 33 are mounted in aligned holes through the base and cover plates 31 and 32 in the same manner as the terminal pins 13 previously described, so as to be held against longitudinal movement within the receptacle, and conducting wires 34 are similarly connected thereto.
The sleeve contacts are slit. as at 36, to enable the lower ends of the sleeve to expand from a contracted position upon the insertion of the terminal pin heads 23 thereinto.
The holes in the receptacle base plate 31 are tapered outwardly, as at 37, to aid the insertion of the terminal pins 13 thereinto. Again, the receptacle base and cover .straight into its respective sleeve contact.
plates are rigidly secured. to one another by any suitable means (not shown).
In the event that there is perfect alignment of the longitudinal axes .of the'terminal pin shanks 2t) and the corresponding sleeve contacts 33, the plug and receptacle may be mated by simply bringing the plug and receptacle together, with each terminal head 23 being inserted Upon such insertion, theconical cap of the head will cam thelower ends of the sleeve contacts apart so that insertion is accomplished quite easily.
In the event that there is misalignment between a terminal pin and contact sleeve, as illustrated in the middle set of contacts in Fig. l, the lateral resiliency of the shank will enable the shank to flex as the head 23 thereon engages the tapered receptacle wall 37 so that the head will be guided into the contact sleeve 333, with the conical tipportion again easing the insertion of the head thereinto. When the plug and receptacle are disconnected, the terminal pin shankwill spring back to its initially straight position, and the shanks of all of the terminal pins will be parallel to one another.
Figs. 2 and 3 illustrate themanner in which the contact area between the terminal heads 23 and the sleeve contacts 33' remains the same in spite of misalignments therebetween. The line a represents the circle of tangency between the conical tip and spherical portions of the head 23, and line b represents the circle of tangency between the head 23 and the contact sleeve 33. If all points on line b are maintained below line a, as in Figs. 2 and 3, then only the spherical portion of the head can be in contact with the contact sleeve 33. Since the line of tangency of a sphere within a cylinder will always occur along a great circle of the sphere, regardless of rotation of the sphere, it is obvious that the areas of contact between the sleeve 33 and head 23 will be'equal in Figs. 2 and 3. Moreover, the amount of spreading of the split sleeve 33'will be the same whether the contacts are aligned orrnisaligned, and, consequently, the same contact pressure between the sleeve and'head will exist in each instance. Thus, by the particular formation of the terminal pin head described, the head is easily in sertable into the sleeve 33, whether aligned or not there with, and, once inserted, the contact area and pressures will be substantially the same, whether alignment exists or not.
A particular advantage of the invention becomes apparent when the same plug is used with difierent receptacles.v As, for example, if a conventional'plug with inflexible pins is inserted into one receptacle in which misalignment exists, then the misaligned pin would be bent in conformity thereto. This would then render the plug unusuable for fully satisfactory results with any other receptacle, unless the bent pin is manually straightened; However, in the present invention, as soon as the plug and receptacle are disconnected, the misaligned. pin will immediately spring back to its original position, ready for another connecting operation.
Another important advantage of the resilient terminal pin shanks in the present invention is that the plug and receptacle are prevented from undue stresses in the event of lateral shifting therebetween or vibrations, because the pin shanks will flex with such movements.
Although the sets of contacts are shown in Fig, 1 as being rather widely spaced from one another for purposes of clarity, it is to be realized that in actual practice the contacts and pins are spaced quite closely to one another, with the closeness of such spacing being limited only by the physical strength and. dielectric properties of the base and cover materials. In any desired spacing, the selfaligning properties of the plug terminals remain eflective.
1n the specific embodiment described, the terminal pin shanks 20 have been described as having a steel core and outer copper layer. Although this particular shank material has been found to give the best results, other materials having the same characteristics may be substituted therefor, or the shank may be a singlematerial. In any event, it is necessary that the shank have good electrically con.- ductive properties and essential that it be sufliciently resilient to be self restoring to its initial straight position, even though. bent therefrom,
It is to berealized further that the form of the invention herewith shown and described is to be taken as the preferred embodiment of the same, and thatv various changes in the shape, size, and arrangement of parts in addition to those referredto above may be made without departing from the spirit of the invention or the scope of the attached claims.
Having thus described my invention, what I claim and desire to secure by Letters Patent is:
l. A self-aligning plug. comprising an electrically nonconductive plug body; an electrically conductive terminal pin rigidly fixed to said body and having an elongated, laterally resilient shank projectingoutwardly from said body, said shank having a bimetallic construction with a highly resilient core and a highly electrically conductive outer shelllbonded thereto; and a conico-spherical shaped head formed on the outer end of said shank and having a conical portion. tapering away from said shank and terminating at an apex to serve as a guide, the apex of said head being in alignment with the longitudinal axis of said shank and with the spherical diameter of said head substantially greaterv than the diameter of said shank.
2. A plug asset forth inclaim 1 wherein said terminal pin shank is formed with a steel core and having an outer shell of copper bondedthereto.
References Cited in the file of this patent UNITED STATES PATENTS 2,269,314 MacDonald Jan. 6, 1942 2,476,886 Miller et al July 19, 1949 2,539,230 Craig Jan. 23,1 1951 2,658,182 Jackson et al Nov. 3,1953 2,748,361 Dixon et a1. May 29; 1956 FOREIGN PATENTS 536,665 Great Britain May 22, 1941 610,347 Great Britain Oct. 14, 1948