US 3425026 A
Description (OCR text may contain errors)
Jan. 28, -1969 G. w. THEuNlssEN V3,425,026
ELECTRICAL CONNECTOR ASSEMBLY `Filed April 5, 1967 PRIOR ART DE VICE PRESENT INVENTION l 'INVENTOR G. w. TH Euu lssEN BY Ww ATTORNEY United States Patent Olce C 39,004 U.S. Cl. 339--90 Int. Cl. H01r 7/32 1 Claim ABSTRACT F THE DISCLOSURE Grooves are provided on an outer surface of one connector for receiving accommodating pinlike members mounted within a shell-like collar on the other connector. The grooves are formed to have an initial relatively steep angle of descent which decreases regularly to a very shallow angle at the opposite end.
The present invention relates generally to an electrical connector assembly, and, more particularly, to a bayonet coupling device for multi-contact electrical connectors in which a rst connector includes pinlike members for receipt within accommodating guide grooves or raceways in the other connector.
Description of the prior arl It is known at this time to connect and secure multicontact connectors to one another by including grooves or slots in one connector within which are received pinlike members carried by the other connector. Of known bayonet connector assemblies of this character, none have been found fully satisfactory in all respects. Certain prior art devices, for example, provide relatively straight-line slots or grooves that have a constant steep angle of descent. In this case, it can be shown that the amount of force necessary to effect connection increases non-linearly, with a maximum value reached at approximately when the electrical contact connection is first made. Since the connecting force is applied by the pinlike members contacting the side walls of the grooves or slots, the end result is considerable wear of the side walls at those portions corresponding to maximum force application. Of course, conlining the wear to relatively small areas is deteriorative of the connector assembly life, particularly when the associated parts are made of materials such as aluminum, as is a usual practice.
Other prior art bayonet connectors which have provided curved grooves or raceways of a sort, have done so in such manner that the complete twist-angle for coupling is relatively small (120 degrees or less for a three-groove and pin assembly) and thereby requiring commensurately large connecting force with resulting wear distributed again, over a relatively small area.
Moreover, since connection is frequently made by hand, it is desirable that the required connecting force be kept low, and not increase abruptly or non-linearly throughout the required range of ap lication and, it is particularly in this regard that the known prior art connector assemblies are deficient.
It is, therefore, a primary object of the present invention to provide a bayonet electrical connector assembly having grooves and mating pins on the different parts, the shape of the grooves being such that the interconnecting force requirement is smooth and regular.
Another object is the provision of a groove and pin electrical connector assembly in which each groove has a continuous curve shape.
A further object is the provision of an electrical con- 3,425,026 Patented Jan. 28, 1969 nector assembly as inthe above objects in which the twistangle to effect connection is in excess of degrees.
Another object is to provide a bayonet electrical connector assembly highly reliable and long-lived in operation, and relatively simple and inexpensive to manufacture.
Summary of the invention Briefly, the electrical connector coupling device of the invention includes a first shell carried by one of the connectors, the outer surface of which shell has a plurality of curved grooves that begin at one end with a relatively steep angle of descent and end With a relatively small angle of descent. Pinlike members carried by the other connector are received within these grooves for joining the connectors together.
Other objects and advantages of the invention will be apparent to those skilled in the electrical connector art on reference to the following description when taken in conjunction with the accompanying drawing.
Brief description of the drawing FIGURE l is a perspective, elevational view of the electrical connector assembly of the invention.
FIGURE 2 is a graph of applied force as a function of twist-angle.
Description of the preferred embodiment With reference now to FIGURE 1, the electrical connector 10 is seen to comprise a receptacle 11 and a plug 12 to be mated therewith. The plug includes a plurality of pin contacts that are received within associated female contacts on the receptacle when assembled.
The receptacle 11 includes an outer cylindrical shell 13 having a plurality of grooves or raceways 14 formed in the outer surface thereof. These grooves receive associated pinlike members 15 that project radially inwardly from the inner surface of a rotatable cylindrical shell or collar 16 carrier by the plug 12. Rotation of the collar 1'6 in the direction of the arrow effects cooperation between the pinlike members and the walls defining the grooves 14 to move the plug toward and into engagement with the receptacle. Rotation of the collar in the direction opposite that indicated by the arrow serves to disengage the plug and receptacle.
In the preferred form described here, the shell 13 is provided with three identical grooves 14 arranged in an equally spaced manner, the entrance portions of which (i.e. the groove openings facing the plug 12) are 120 degrees apart when viewed along the shell axis. The pin members 15 are similarly located at 120 degree intervals on the collar.
Each groove has a generally rectangular cross-section and extends along a path that is continuously curved. More particularly, each groove at its entrance end possesses a relatively steep angle of descent, a, which angle gradually and in a continuous manner decreases until at the inner reaches of the groove it is substantially zero, or at most a few degrees (indicated by the angle b). Functionally the result achieved by this special curvature of the grooves, is that when the members 15 are first introduced into the grooves there is little force opposing joinder of the plug and receptacle so that the two may be drawn toward one another rapidly with little twisting force on the collar 16 required. As the plug is brought to the position where the male contacts iirst begin to be inserted in the female contacts of the receptacle, the required turning force rises sharply. That is, not only is it necessary to overcome the increasing reaction of a spring 17 which is being compressed, but the sudden frictional engagement of the male and female members must be handled. However, through the specified change in curvature and angle of descent of the grooves there is provided a correspondingly greatly increased mechanical advantage to the members acting on the groove walls, so that no abrupt increase in torque requirement is noted at the collar 16.
Each groove can terminate at its innnermost end in a pocket 18 that is slightly larger across than the groove width. When the pin members come to rest in these pockets, the spring 17 will tend to move the members toward the top of the pockets serving to lock them in place.
Although some variation of entrance angle of descent and rate of change of slope may be used and still fall within the general spirit of this invention, best results have been obtained with the initial or entrance descent angle lying in the range of about 18-27 degrees. Also, the ratio of groove length to groove depth of travel D has been found to be important, with linear applied twisting force obtained when this ratio is in the range of about 4.5-6.0.
A still further aspect of the invention is the relatively small total amount of twist angle necessary to join (or disengage) the plug or receptacle. For devices constructed with the above-stated entrance descent angles and groove length/depth of travel ratio, these twist angles are in the range of about 18S-210 degrees. The importance of this feature will be appreciated in considering twist angle requirements of some modified structures that do not practice the invention. For example, an obvious expedient to reduce twisting-force would be to connect the plug and receptacle by means of a conventional line pitch screw thread. However, in that case the required twist angle would be quite large, with most of the turning accomplishing nothing more than to move the receptacle and plug toward one another. On the other hand, if steep slope grooves are used alone, the twist angle can be reduced, but only at the expense of having an undesirable connecting torque characteristic.
The graph in FIGURE 2 illustrates comparative performance of the invention as against a connector assembly having sloping relatively straight grooves. It will be noted that the curve of necessary applied force for the prior art device rises sharply upwardly toward the end of the engagement process. In contrast, the force requirements of the device of this invention are at least linear and can even produce a condition where the required force per unit of twist angle begins to decrease in the final phase of engagement.
There is accordingly provided in the practice of this invention a bayonet-type pin and socket connector assembly requiring relatively low force application per unit twist angle to effect connection. Due to the elimination of abrupt force requirements, the wear on pins and associated raceways of the connector assembly is considerably reduced, as well as being distributed over relatively large areas of the raceway walls rather than confined to one locality.
While only a single embodiment of the invention has been described and illustrated, it should be understood that various other modifications and variations will come to the mind of one skilled in the electrical connector art. In this connection it should be noted that whereas three raceways or grooves were used in the description, there could, of course, be more than three, or for that matter, in a particular situation two such grooves might be satisfactory.
What is claimed is:
1. An electrical connector comprising: plug and socket means requiring a predetermined mating force; a rotatable cap on one of said means having a plurality of inwardly extending projections; and a groove for each projection on the outside of the other means, each groove having an opening at one end to receive a corresponding projection, each groove having a pitch at said one end substantially greater than that at the other end thereof, the pitch of each groove at said other end being substantially zero, the pitch of each groove at said one end being within the range of 18 to 27 degrees, the ratio of the length of each groove to the axial extent thereof being within the range of 4.5 to 6.0.
References Cited UNITED STATES PATENTS 61,607 1/1867 Craig 285-362 149,728 4/1874 Diehl et al 285-361 2,039,037 4/1936 Simpson 220-40 3,165,220 1/1965 Haynes 21S-42 FOREIGN PATENTS 1,195,451 11/1959 France.
MARVIN A. CHAMPION, Primary Examiner.
JOSEPH M. MCGLYNN, Assistant Examiner.
U.S. Cl. X.R.