Patent Publication Number: US-7914347-B2

Title: Low resistance connector for printed circuit board

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates generally to low resistance connectors for printed circuit boards, and particularly to connectors that require lower resistance to unmate the connector from printed circuit boards and only when the unmating of the connector from the printed circuit board is desired. 
     2. Technical Background 
     Coaxial connectors are used to connect with electrical connectors on printed circuit boards (PCBs). The electrical connectors on the PCBs are soldered to metallic traces on the PCBs, which in turn are laminated to the board material. Typical electrical connections between the PCB connector and coaxial connectors are of the push-pull type. These connections are known to cause a delamination of the soldered connections and the metallic traces on the PCBs themselves when the connectors are unmated due to the typically higher resistance required to unmate them. 
     Prior coaxial connectors used on PCBs have attempted to solve this problem by making the connection between the coaxial cable and the electrical connector easier to unmate (easier to pull), but that allowed the coaxial cable to become unmated when it was not desired, causing an unwanted interruption of the electrical systems. 
     It would be desirable therefore to provide an electrical connector that can be used on PCBs that allows for easy unmating of the connector only at desired times. 
     SUMMARY OF THE INVENTION 
     Disclosed herein is an electrical connector for a printed circuit board that includes a main body having a forward portion and a rearward portion, a front end and a back end and an opening extending therebetween, the front end disposed on the forward portion and the back end disposed on the rearward portion; the forward portion having a generally circular cross section, the forward portion having at least one inclined surface extending from the front end to a middle portion of the forward portion, and at least one generally straight portion adjacent the inclined surface creating a ledge between the inclined surface and the straight portion. 
     In some embodiments, the electrical connector has two inclined surfaces, two generally straight portions and two ledges. 
     In some embodiments, there is a transition portion between the generally straight portion and the outer surface of the forward portion. 
     In another aspect, an electrical connector is disclosed for connecting a printed circuit board and a coaxial cable that includes a first connector body having a forward portion and a rearward portion, a front end and a back end and an opening extending therebetween, the front end disposed on the forward portion and the back end disposed on the rearward portion, the forward portion having a generally circular cross section, the forward portion having at least one inclined surface extending from the front end to a middle portion of the forward portion, and at least one generally straight portion adjacent the inclined surface creating a ledge between the inclined surface and the straight portion and a second connector body having an outer sleeve, the sleeve having a front end and a back end and an opening therebetween, the opening configured to receive at least a portion of the forward portion of the first connector body, the outer sleeve having a least one arm extending between the front end and a middle portion and configured to engage the inclined portion and ledge of the forward portion to prevent axial movement of the first and second connector bodies relative to one another when the first connector body is disposed in the second connector body opening. 
     Additional features and advantages of the invention will be set forth in the detailed description which follows, and in part will be readily apparent to those skilled in the art from that description or recognized by practicing the invention as described herein, including the detailed description which follows, the claims, as well as the appended drawings. 
     It is to be understood that both the foregoing general description and the following detailed description present embodiments of the invention, and are intended to provide an overview or framework for understanding the nature and character of the invention as it is claimed. The accompanying drawings are included to provide a further understanding of the invention, and are incorporated into and constitute a part of this specification. The drawings illustrate various embodiments of the invention, and together with the description serve to explain the principles and operations of the invention. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a perspective view of one embodiment of an electrical connector according to the present invention in an unmated position; 
         FIG. 2  is a perspective view of the electrical connector of  FIG. 1  in a partially engaged position; 
         FIG. 3  is a cross sectional view of the electrical connector of  FIG. 1  in a fully engaged position; 
         FIG. 4  is a cross sectional view of the electrical connector of  FIG. 1  with the two bodies slightly rotated relative to one another; 
         FIG. 5  is a cross sectional view of the electrical connector of  FIG. 1  with the two bodies rotated relative to one another which allows the bodies to be separated with little force; 
         FIG. 6  is a cross sectional view of another embodiment of a second connector body of an electrical connector according to the present invention; 
         FIG. 7  is a cross sectional view of yet another embodiment of a second connector body of an electrical connector according to the present invention; and 
         FIG. 8  is a schematic of a PCB board that can be used with the electrical connector. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Reference will now be made in detail to the present preferred embodiment(s) of the invention, examples of which are illustrated in the accompanying drawings. Whenever possible, the same reference numerals will be used throughout the drawings to refer to the same or like parts. 
     Referring to  FIGS. 1 and 2 , an electrical connector  10  has a first connector body  12  and a second connector body  14 . The first connector body  12  has a forward portion  16  and a rearward portion  18 . The forward portion  16  has a front end  20  and the rearward portion  18  has a back end  22 , with an opening  24  extending therebetween. The forward portion  16  has a generally circular cross section with at least one inclined surface  26  extending from the front end  20  toward a middle portion  28  of the front portion  16 . The inclined surface  26  inclines toward the outer surface  30  of first connector body  12  from the front end  20 . The inclined surface  26  transitions into the outer surface  30 , where there is a generally straight portion  32  that creates a ledge  34  between the generally straight portion  32  and outer surface  30 , that in turn is adjacent the inclined surface  26 . As illustrated in the figures, there are preferably two inclined surfaces  26 , two generally straight portions  32 , and two ledges  34 . However, only one, or more, may be present and still come within the scope of the invention. 
     The generally straight portion  32  transitions into the outer surface  30  of the first connector body  12  at transition portions  36  at either end of the generally straight portion  32 . The transition portions  36  have a radius that is preferably different from the diameter of the outer surface  30  of the first connector body  12 . Preferably, the radius of the transition portion  36  is about 0.025 inches, but could range anywhere from 0.00 inches to 0.050 inches. The radius of the transition portion  36  is important for the operation of the electrical connector  10 , as described in more detail below. It should also be noted that the radius and range of the radius can vary with size of the connector. 
     The rearward portion  18  of first connector body  12  also has a generally circular cross section and has a diameter that is generally smaller than that of the forward portion  16 . However the diameter of rearward portion  18  may also be the same as or larger than the radius of the forward portion  16 . As is best illustrated in  FIG. 3 , the first connector body  12  may also have a center contact  40  and a dielectric member  42  to hold and center the center contact  40 . The back end  22  of rearward portion  18  of the first connector body  12  and the center contact  40  are soldered to the PCB as is known in the art. For example as illustrated in  FIG. 8 , a PCB  90  is illustrated. The PCB  90  has an opening  92  into which the center contact  40  is soldered so that it makes contact with the signal metallization  94  and the back end  22  is soldered to the ground metallization  96 . The metallizations  94 ,  96  are then electrically connected to metal traces. 
     The electrical connector  10  also includes the second connector body  14 . Second connector body  14  has an outer sleeve  60  with a front end  62  and a back end  64  and an opening  66  extending therebetween. The outer sleeve  60  may be knurled or grooved to assist in gripping the second connector body  14 . The second connector body  14  has a middle portion  68 , where two cantilevered arms  70  extend toward the front end  62 . The arms  70  are essentially a portion of the outer sleeve, as the arms  70  have the same outer diameter as the remainder of the outer sleeve  60  and are defined by two slots  72  extending from the front end  62  to the middle portion  68 . The opening  66  preferably has two portions, a front inner portion  74  and a rear inner portion  76 . See  FIG. 3 . The front inner portion  74  has a first diameter that is larger than the second diameter of the rear inner portion  76 , thereby creating a forward facing surface  78  in the middle portion  68 . The rear inner portion  76  is configured to receive a cable adapter, center contact and dielectric  80 . The cable adapter, center contact and dielectric  80  are standard parts, known to those of skill in the art. The second connector body  14  is attached to a cable (not shown) and the cable adapter in a standard way. 
     The arms  70  are, by their nature, flexible and are able to flex outward (away from the opening  66 ). The arms  70  preferably have at the front end  82  a downward extending projections  84  (and, in particular, rearward facing surfaces  88 ) that engage the ledge  34  of the first connector body  12 . Preferably, the arms  70  also have a chamfered portion  86  on the front end  82  to assist in guiding the arms  70  onto the at least one inclined surface  26 . As the forward portion  16  of first connector body portion  12  is inserted into the opening  66  of the second connector body  14 , the arms  70  engage the inclined surface  26  (see  FIG. 2 ) and are flexed outwardly. As the two connector bodies are moved relative to one another, the arms  70  are flexed further outward until the downward extending projections  84  go over the ledge  34  and make contact with the generally straight portion  32 . The engagement of the downward extending projections  84  with the ledge  34  prevents the second connector body  14  from being pulled axially away from the first connector body  12 . 
     With the ledge  34  and the rearward facing surfaces  88  of downward extending projections  84  engaging one another, the two connector bodies  12 ,  14  cannot be pulled apart and the force required to connect them to one another is very low. To unmate the first and second connector bodies  12 ,  14 , the user must merely rotate the connector bodies  12 ,  14  relative to one another. As illustrated in  FIG. 3 , the two connector bodies  12 ,  14  are fully engaged.  FIG. 4  illustrates that the two connector bodies  12 ,  14  have begun to be rotated relative to one another. As the arms  70  rotate and move along the generally straight portion  32 , the arms  70  begin to flex outward. As the arms  70  approach the transition portions  36 , the arms  70  flex outwardly even more. The larger the radius of the transition portions  36 , the easier the arms  70  move from the generally straight portion  32  to the outer surface  30 . When the arms  70  make contact with the outer surface  30  that has a constant radius (see  FIG. 5 ), the second connector body  14  can be moved axially relative to the first connector body  12  and unmated with little force (generally limited to the friction of the downward extending projections  84  on the first connector body  12 ). 
     An alternative embodiment of a second connector body  114  is illustrated in  FIG. 6 . The second connector body  114  is similar to the second connector body  14  discussed above, but has an elastomeric gasket  120  that engages the forward facing surface  178  in the middle portion  168 . The elastomeric gasket  120  is preferably impregnated with metallic particles to assist in preventing leakage of the electrical signal from the connector. The elastomeric gasket  120  allows the connector to be sealed against the elements when the first connector body is inserted into the opening  166  and the front end of the first connector body engages the elastomeric gasket  120  and compresses it against the forward facing surface  178 . 
     As illustrated in  FIGS. 3-5  above, the ledge  34  and the rearward facing surfaces  88  of downward extending projections  84  of connector  10  are illustrated as being perpendicular to its axial axis. However, it is possible that the ledge  34  and the rearward facing surfaces  88  of downward extending projections  84  are slanted in a rearward direction to allow for easier engagement of the ledge  34  by the rearward facing surfaces of downward extending projections  84 . For example, as illustrated in  FIG. 6 , rearward facing surfaces  188  of downward extending projections  184  have an angle other than 90 degrees with the front inner portion  174  (the ledge  34  would have a corresponding angle, but is not illustrated). Such a configuration compensates for any variations in the tolerances of the first and second connector bodies. 
     Another alternative embodiment of a second connector body  214  is illustrated in  FIG. 7 . The second connector body  214  has a wave spring washer  220  also disposed against the forward facing surface  278  in the middle portion  268 , where it further limits the axial movement of the connector bodies relative to one another. 
     It will be apparent to those skilled in the art that various modifications and variations can be made to the present invention without departing from the spirit and scope of the invention. Thus it is intended that the present invention cover the modifications and variations of this invention provided they come within the scope of the appended claims and their equivalents.