Compatible trailer connection

A socket connector which can accommodate a first plug connector or a second plug connector has a cylindrical cavity with a first plurality of socket contacts and a second plurality of socket contacts. The second plurality of socket contacts are shorter than the first plurality of socket contacts. The first plug connector has a number of plug contacts arranged for mating engagement with both the first plurality of socket contacts and the second plurality of socket contacts. The second plug connector contains a number of plug contacts arranged only for mating engagement with the first plurality of socket contacts. The socket connector is constructed and arranged so as to allow penetrating travel of the first plug connector fully into the cylindrical cavity so as to engage with the plug contacts the first plurality of socket contacts and the second plurality of socket contacts while limiting penetrating travel of the second plug connector into the cylindrical cavity to a point at which the plug contacts engage the first plurality of socket contacts but the second plurality of socket contacts are neither engaged nor contacted by the second plug connector.

The invention relates generally to making electrical connections between 
the tractor and the trailer of a tractor-trailer rig, and more 
particularly concerns connecting that is compatible with connectors having 
first and second different numbers of contacts, typically seven and 13. 
A standard connector presently used within the industry is a 
seven-conductor connector; i.e., a connector capable of connecting seven 
separate circuits. Present sizing and geometric standards are set forth as 
SAE J560b, in "Seven- Truck-Trailer Jumper Cable," 1992 SAE Handbook, p. 
2:20.137. Another standard connector is capable of interconnecting 13 
circuits. 
Generally speaking a connector has two primary parts, a receptacle socket, 
or female, connector and a cable plug, or male, connector. The socket, or 
female connector has within its cavity a plurality of metal contact pins, 
or male contacts. The cable plug, or male, connector has within its 
terminal end a plurality of small, cylindrical, metal cavities, or female 
contacts. The plug connector is inserted into the cavity of the socket 
connector and the pins of the socket connector fit into the female 
contacts within the plug connector, thereby completing the various 
electrical circuits wired to the connector. 
A preliminary novelty search of subclasses 34-36, 51, 144 and 501 of class 
439 uncovered U.S. Pat. Nos. 3,601,660, 3,915,476, 4,249,125, 4,405,190, 
4,460,811, 4,669,791, 4,770,644, 4,792,308 and 4,846,697. U.S. Pat. No. 
4,842,532 discloses a compatible connector with offset portions carrying 
additional connections. 
In the trucking industry, one particular tractor may pull many different 
trailers at different times; and one particular trailer may be pulled by 
many different tractors at different times. It is therefore highly likely 
that a tractor equipped with a seven-conductor socket connector will 
sometimes couple to a trailer equipped with a 13-conductor plug connector; 
or that a tractor equipped with a 13-conductor socket will couple to a 
trailer equipped with a seven-conductor plug. 
It is accordingly an important object of this invention to provide a socket 
connector and a plug connector each containing a first number of contacts, 
such as 13, greater than a second number of contacts, such as seven, but 
each of which maintains interconnecting compatibility with a plug or 
socket connector, respectively, having the second number of contacts. 
According to the invention, there is a socket connector which can 
accommodate a first plug connector having a first array of a first 
plurality of contacts or a second plug connector having a second array of 
a second plurality of contacts different from said first plurality. The 
socket connector has a cylindrical cavity having the first plurality of 
contacts arranged in a pattern that mates with the first plurality of 
contacts in the first plug connector and the second plurality of contacts 
arranged in a pattern that mates with the pattern of the second plurality 
of contacts in the second plug connector. The socket connector is 
constructed and arranged to allow penetrating travel of the first plug 
connector fully into the cylindrical cavity so as to engage both the first 
plurality of contacts and the second plurality of contacts while limiting 
penetrating travel of the second plug connector into the cylindrical 
cavity to a point at which the first plurality of contacts are engaged but 
the second plurality of contacts are free from engagement and contact with 
the second plug connector. Typically, the first plurality of contacts form 
a pattern with a first of the contacts coaxial with the axis of the 
cylindrical cavity and the remaining ones of the latter contacts 
positioned equidistant from and symmetrically disposed about the 
cylindrical cavity axis, typically equiangularly spaced about the 
cylindrical axis.

With reference now to the drawing, and more particularly to FIGS. 1, 2, 6, 
and 7, there is shown in FIG. 1 an end view of an embodiment of socket 
connector 10 of the invention containing thirteen male contact pins. 
Socket connector 10 has a housing 11 with a cylindrical cavity 12. Located 
within and projecting from the rear of cavity 12 are thirteen male contact 
pins positioned circumferentially about, and parallel to, axis 13 of 
cavity 12. Seven standard pins 14 are positioned in a standard pattern as 
set forth by SAE J560b, i.e., a central pin surrounded by six pins spaced 
equiangularly from each other and from axis 13 of cavity 12. Per the SAE 
J560b standard, the pin 14A located at the 12 o'clock position in FIG. 1 
is slightly larger in diameter than the rest of standard pins 14. Also 
located within cavity 12 and projecting from the rear of the cavity 12 are 
six supplemental male contact pins 15 positioned circumferentially about 
and parallel to axis 13 of cavity 12. Supplemental male contact pins 15 
are of smaller diameter and project a shorter distance than standard male 
contact pins 14. Supplemental male contact pins 15 are positioned 
equidistant from axis 13 of cavity 12 just outside standard male contact 
pins 14. Supplemental male contact pins 15 are positioned angularly 
between standard male contact pins 14. Wiring from the various circuits is 
connected at the rear of socket connector 10 to standard male contact pins 
14 using set screws 21, or directly to the supplemental male contact pins 
15 using commercially available female connectors (not shown). 
Socket connector 10 has a cover 16, spring biased towards the closed 
position. Cover 16 has a latch slot 17 and a latch-tab 18. Gasket 19 seals 
cavity 12 when cover 16 is in the closed position. An indexing key slot 
20, which is a shallow, narrow channel in the wall of cavity 12, runs 
parallel to axis 13 of cavity 12. Indexing key slot 20 does not extend to 
the rear of cavity 12. 
Referring now to FIGS. 3-5, plug connector 40 of the invention is shown. 
Plug connector 40 comprises a cylindrical housing. Terminal insulator 
surface 50 of plug connector 40 has a pattern of portals containing the 
female contacts. Seven standard female contacts 51 are positioned in a 
standard pattern as set forth by SAE J560b; i.e., a central contact 
surrounded by six contacts positioned angularly about axis 53 of plug 
connector 40 spaced equiangularly from each other and from axis 53 of plug 
40. Per SAE J560b, female contact 51A located at the 12 o'clock position 
in FIG. 5 is slightly larger in diameter than the rest of standard female 
contacts 51. Six supplemental female contacts 52 are positioned 
circumferentially about axis 53 of plug 40 equidistant from axis 53 just 
outside the circle of standard female contacts 51, and angularly between 
the circle of standard female contacts 51. Supplemental female contacts 52 
are of a smaller diameter than standard female contacts 51. 
At the 12 o'clock position in FIG. 5, there is shown an indexing key 54 
which runs axially along plug connector 40 from a position slightly aft of 
terminal surface 50 to a point approximately midway along axis 53 of plug 
40. There is also a latch post 55, circumferentially located at the same 
position as indexing key 54 and toward the end of the plug opposite the 
terminal insulator surface 50. 0-ring 56 is located slightly behind 
terminal insulator surface 50, in an annular groove on the exterior 
surface of plug 40. 
Plug 40 is constructed so that wiring from the various circuits to be 
connected, contained within a thirteen-conductor cable 56A, enters plug 40 
at the rear of the plug, and is affixed to the female contacts 51, 52. 
Referring now to FIGS. 6-8, the use of the invention may be seen. FIG. 6, 
shows plug connector 40 of the invention used in conjunction with socket 
connector 10 of the invention. Cover 16 is held open, and plug 40 is 
positioned so that indexing key 54 is aligned with indexing key slot 20, 
and plug 40 enters cavity 12 of socket connector 10. Because indexing key 
54 does not extend to terminal surface 50 of plug 40, plug 40 can slide 
fully into the cavity 12, with terminal surface 50 of plug 40 contacting 
the rear of cavity 12. Standard female contacts 51 fully engage standard 
male contact pins 14, and supplemental female contacts 52 fully engage 
supplemental male contact pins 15. Latch slot 17 latches over latch post 
55, thereby securing plug connector 40 within socket connector 10. 
FIG. 7 shows an SAE J560b standard seven-pin plug connector used in 
conjunction with socket connector 10 of the invention. Because the 
indexing key on a standard SAE J560b plug connector extends to the 
terminal insulator surface of the plug, and because indexing key slot 20 
of socket connector 10 of the invention does not extend to the rear of 
cavity 12, a standard seven-pin plug connector can enter cavity 12 only to 
the point at which the indexing key of the plug abuts the end of indexing 
key slot 20 of socket connector 10 of the invention. This feature prevents 
the terminal insulator surface of the standard seven-pin plug connector 
from contacting and crushing supplemental male contact pins 15, which are 
not shown in FIG. 7. Because standard male contact pins 14 are longer than 
supplemental male contact pins 15, the seven female contacts within the 
standard plug can engage standard male contact pins 14. Latch tab 18 
engages the plug connector behind the indexing key, thereby securing the 
standard plug connector within socket connector 10. 
FIG. 8 shows plug connector 40 of the invention used in conjunction with a 
standard SAE J560b seven-pin socket connector. Plug connector 40 fully 
enters the cavity of the standard socket connector, such that terminal 
insulator face 50 of plug connector 40 abuts the rear surface of the 
cavity. Standard female contacts 51 engage the seven male contact pins of 
the standard socket connector. A latch tab on the cover of the standard 
socket connector engages the rear of indexing key 54, thereby securing 
plug connector 40 in the standard socket connector. 
There has thus been described a novel electrical connector consisting of a 
plug connector and a mating socket connector, each having more electrical 
contacts than an analogous standard connector, but each being matingly 
compatible with the corresponding mating standard connector having fewer 
electrical contacts. It is evident that those skilled in the art may now 
make numerous uses and modifications of and departures from the specific 
embodiment described herein without departing from the inventive concepts. 
Consequently, the invention is to be construed as embracing each and every 
novel feature and novel combination of features present in or possessed by 
the apparatus and techniques herein described and limited solely by the 
spirit and scope of the amended claims.