Abstract:
An electrical connector, of the pin/socket type, wherein the pin is removable from the socket. Ordinarily, physical movement of the connector causes the contact points between the pin and the socket to redistribute themselves, with deleterious results. The invention constrains the pin to remain in contact with two rail surfaces defined in the socket. As a visual analogy, the pin can be viewed as a large cylindrical tank, supported by railroad tracks parallel with the tank&#39;s axis. Cradling the pin in this manner reduces, or eliminates, redistribution of contact points.

Description:
TECHNICAL FIELD  
         [0001]    The invention concerns electrical connectors, particularly of the pin-and-socket type, which contain a spring which biases a pin into contact with the socket. The invention exhibits (1) improved reduction in arcing, and (2) less movement of pin/socket contact points during physical movement of the connector.  
         BACKGROUND OF THE INVENTION  
         [0002]    [0002]FIG. 1 illustrates a commercial aircraft  3 . Block  6  represents a gas turbine aircraft engine, block  9  represents an electrical alternator powered by the engine  6 , elements  12  represent electrical cables connected to the alternator  9 , and block  15  represents an electrical connector interconnected within the cable  12 .  
           [0003]    [0003]FIG. 2 represents schematically the cylindrical socket  18 , and a leaf spring  21 . FIG. 3 shows the components of FIG. 2 in assembled form, and FIG. 4 illustrates a bull-nose, or dome-nose, pin  24 , which mates with the socket  18 . FIG. 5 is a cross-sectional view of the pin/socket assembly  30 , showing pin  24  positioned within the socket  18 , with leaf spring  21  biasing the pin  24  into contact with the socket  18 .  
           [0004]    The connector  15  in FIG. 1 contains one pin/socket assembly  30  for each wire, not individually shown, within the connector  15 .  
           [0005]    The Inventors have observed what appears to be premature breakage in the leaf spring  21 , and other damage to the pin/socket assembly  30 .  
         SUMMARY OF THE INVENTION  
         [0006]    One form of the invention comprises two parallel rail surfaces, perhaps supported on the internal walls of a socket, and a leaf spring parallel with the rails. A pin is also parallel with the rail surfaces. A spring biases the pin into contact with the rail surfaces. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0007]    [0007]FIG. 1 illustrates an aircraft  3  and a schematic representation of an electrical component such as a generator  9  within an engine  6  of the aircraft  3 .  
         [0008]    [0008]FIG. 2 illustrates a socket  18  of an electrical connector, together with a leaf spring  21 .  
         [0009]    [0009]FIG. 3 illustrates the apparatus of FIG. 2 in cutaway view.  
         [0010]    [0010]FIG. 4 illustrates the apparatus of FIG. 3, together with a pin  24  which inserts into the socket  18 .  
         [0011]    [0011]FIG. 5 is a cross-sectional view of the apparatus of FIG. 4 in assembled form.  
         [0012]    [0012]FIGS. 6 and 7 illustrate, in exaggerated form, how the pin  24  can move within the socket  18 .  
         [0013]    [0013]FIG. 8 is a cross-sectional side view of the apparatus of FIG. 4 in assembled form.  
         [0014]    [0014]FIGS. 9 and 10 illustrate, in exaggerated form, how the pin  24  can move within the socket  18 .  
         [0015]    [0015]FIGS. 11 and 12 illustrate one form of the invention.  
         [0016]    [0016]FIG. 13 illustrates another form of the invention.  
         [0017]    [0017]FIGS. 14 and 15 illustrate a type of free-body diagram illustrating behavior of the apparatus of FIG. 5.  
         [0018]    [0018]FIG. 16 illustrates another form of the invention.  
         [0019]    [0019]FIGS. 17 and 18 illustrate a type of free-body diagram illustrating behavior of the apparatus of FIG. 16 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0020]    As stated above, the Inventors have identified damage occurring to the pin/socket assembly  30  of FIG. 4. While the precise mechanisms and agencies responsible for the damage may be difficult to identify, several possible sources of damage are the following.  
         [0021]    One source is physical movement of the pin  24  within the socket  18 , and the results which the movement causes. During operation of the aircraft  3 , the connector  15  is subject to movement, due to vibration, and also due to bodily movement of the connector  15  itself, as when the aircraft  3  undergoes a maneuver, or other operations causing relative motion between mating hardware. During a maneuver, such as landing, G-forces arise which move the connector  15 .  
         [0022]    This movement and vibration can cause the pin  24  to move with respect to the socket  18 . For example, FIG. 6 shows the pin  18  displaced leftward, and FIG. 7 shows the pin  18  displaced to the right. In addition, other types of movement are possible. FIG. 8 is a cross-sectional view of the pin  24  within the socket  18 , in the ideal configuration. However, movement of the connector  15  can cause the pin  24  to skew, as shown in FIGS. 9 and 10. The ends of the pin  24  become separated from the socket  18 , as indicated by gaps  33  and  36 .  
         [0023]    [0023]FIGS. 9 and 10 illustrate a movement of the pin  24  which may be termed pitch, as that term is used in the aircraft industry. A similar type of movement is termed yaw, which can be viewed as pitch in the left-right direction. The pin  24  may experience yaw as well.  
         [0024]    The movements just described have a complex effect on the electrical current flowing through the pin/socket assembly  30 . When movement occurs, the points of contact between the pin  24  and socket  18  shift. For example, when the pin  24  is positioned as shown in FIG. 10, a point contact occurs at point  39 . When the pin  24  is positioned as shown in FIG. 8, surface contact occurs. The point contact of FIG. 10 is a high-resistance flowpath for electrical current, which causes increased current to flow through the spring  21 .  
         [0025]    Thus, movement of the pin  24  between the two positions results in increased current in the spring  21 , followed by a decrease.  
         [0026]    This current can heat the spring  21 , and re-temper the metal, resulting in loss of clamping force. Further, loss of the clamping force can make the excursions to the positions shown in FIGS. 9 and 10 easier for the pin  24 , because the spring  21  is now weaker, thereby promoting additional overheating of the spring  21 .  
         [0027]    Therefore, a possible cause of breakage of spring  21  is re-tempering because of heating due to sporadic high electrical currents passing through the spring.  
         [0028]    In addition, at the microscopic level, the surfaces of the pin  24  and socket  18  in general are not smooth, but can be represented as miniature mountain ranges. At the microscopic level, the surfaces are rough, like sandpaper. When two surfaces roll, or slide, as in shifting from the situation shown in FIG. 6 to that in FIG. 7, the peaks scrape and roll against each other, causing arcing.  
         [0029]    The arcing is worsened if the connector  15  is connected directly to the alternator  9 , as opposed to being connected to a power supply powered by the alternator which provides DC power. The reason is that, if connected directly to the alternator, the connector  15  is connected to electrical coils. The coils have large inductances. When the arcing occurs, the current through the coils is momentarily interrupted. The interruption causes the well known flyback voltage. The flyback voltage is high, worsening the arcing.  
         [0030]    Visible arcing is produced by ionization of the air located in the vicinity of the rough points, on the surfaces of the pin  24  and socket  18 . As is well known, a sharp point on a charged conductor is a source of very high electric fields. These electric fields can strip electrons away from air molecules. The visible arcing represents radiation produced by these electrons in falling back into the charged nuclei of the air molecules. That is, the removed electrons return to a lower energy state, and radiate photons in the process. This process is very similar to many processes found in ordinary combustion.  
         [0031]    Thus, while each event of visible arcing may be small, and the events may be intermittent, the collective effect of numerous arcing events over time causes heating, pitting, corrosion, and other types of weakening damage to the pin/socket assembly  30 .  
         [0032]    The invention mitigates the damage just discussed.  
         [0033]    [0033]FIGS. 11 and 12 are cross-sectional views of two forms of the invention. Pin  50  is contained within a triangular socket  53 . Spring  56  biases the pin  50  into contact at points  59  and  62 . Pigtails  60  and  61  represent cables analogous to cables  12  in FIG. 1. Under this arrangement, the rolling described in connection with FIGS. 6 and 7 is significantly restricted.  
         [0034]    [0034]FIG. 13 is a schematic representation of the apparatus of FIGS. 11 and 12. In effect, a V-surface  64  contacts the pin  50 . Contact is made along contact lines  67  and  68 , representing tangent points of the pin  50 .  
         [0035]    Some significant features of the arrangement will be discussed.  
         [0036]    The prior art device of FIG. 5 can be represented as shown in FIG. 14, where the socket  18  of FIG. 5 has been replaced by flat surface  75 , for ease of explanation. One justification for the flat surface  75  is that the flat surface  75  is still cylindrical, like socket  18 , but of a large diameter. Arrow  78  in FIG. 14 represents the force applied by the spring  21  of FIG. 5. Line  80  is a reference line, to show rotation.  
         [0037]    When the pin  24  rolls as indicated in FIG. 15, the force  78  is no longer applied to the 12 o&#39;clock position. In fact, as shown in FIG. 15, the force  78  actually promotes further rolling, because the pin  24  reacts to the force  78  along a radius. That radial reaction force has horizontal and vertical components. The horizontal component promotes further rolling.  
         [0038]    Of course, the degree to which further rolling is promoted depends on (1) the width of the spring  21 , and (2) whether it is constrained to always apply a downward force in FIG. 14.  
         [0039]    Therefore, depending on the detailed design of the spring  21 , the situation of FIG. 14 can represent an unstable equilibrium.  
         [0040]    In contrast, one form of the invention may be viewed as shown in FIG. 16. The contact lines  67  and  68  of FIG. 13 are provided by elongated rails, or rail surfaces,  85  and  86  in FIG. 16, which extend into the paper. Arrow  90  in FIG. 17 represents the force applied by the spring  56  of FIG. 16. If the pin  50  attempts to rotate to the position shown in FIG. 18, arrow  90 , shown in its original position, provides a restoring force, tending to restore the pin  50  to the position shown in FIG. 17. The equilibrium is stable.  
         [0041]    The invention eliminates, or substantially reduces, surfaces along which the pin  50  can roll. For example, as shown in FIG. 6, the prior art pin  24  can roll up the socket  18 . The movement is similar to that of an internal pinion gear inside a ring gear. As in the ring/pinion gears, any rotation of the pin  24  is accompanied by physical displacement of the pin  24 , unless slippage occurs.  
         [0042]    In contrast, as FIG. 17 indicates, if pin  50  attempts to rotate into the position shown in FIG. 18, rotation only occurs about point  95 .  
         [0043]    Restated, in FIG. 6, when pin  24  rolls, it climbs the wall of socket  18 , unless slippage occurs. From an arcing point of view, both climbing and slippage are deleterious. In contrast, in FIG. 18, rotation of pin  50  is inhibited by spring force  90 . If rotation occurs at all, it is about the line represented by point  95 . But the contact between pin  50  and line  95  is essentially the same as before. From an arcing perspective, the situation is vastly improved.  
         [0044]    [0044]FIG. 16 illustrates the elements  56 ,  85 , and  86  in contact with the pin  50 . Those elements are supported by a support system  98 , which can take many forms, such as that shown in FIGS. 11 and 12. As another example, the support system can take the form of a cage, or exoskeleton. As another example, the socket  53  of FIG. 12 can contain embossments or rods, which perform the function of rails  85  and  86  in FIG. 16. The internal surface of socket  53  can be egg-shaped.  
         [0045]    [0045]FIG. 16 illustrates electrical contact with the pin  50  at three positions on the circumference of the pin  50 . These three positions are circumferentially displaced from each other. These three positions are a cross-sectional representation of three elongated lines, or regions, of contact. Two regions are represented by lines  67  and  68  in FIG. 13, and the other is represented by the length of contact along spring  56 . Pin  50  is cradled by the rail surfaces represented by lines  67  and  68 , and is biased into contact with those surfaces by spring  56 .  
         [0046]    [0046]FIG. 8 illustrates an analogous contact with a spring  21 .  
         [0047]    Numerous substitutions and modifications can be undertaken without departing from the true spirit and scope of the invention. What is desired to be secured by Letters Patent is the invention as defined in the following claims.