Patent Publication Number: US-6663439-B2

Title: Electrical connector with spring biased contacts

Description:
RELATED APPLICATIONS 
     This application is related to, and claims priority from, Provisional Application No. 60/272,978 filed Mar. 2, 2001, titled “Spring Probe Electrical Connector”, the complete subject matter of which is incorporated herein by reference in its entirety. 
    
    
     BACKGROUND OF THE INVENTION 
     Certain embodiments of present invention relate to an electrical connector for interconnecting electronic components, such as a battery and printed circuit board. More particularly, certain embodiments of the present invention relate to an electrical connector having spring-biased plunger contacts for an electrical connector. 
     In certain applications, such as a cell phone with a charger, a battery in the cell phone is electrically connected to a printed circuit board in the charger to be recharged when the cell phone is placed in the charger. Typically, the charger includes an electrical connector with spring-biased plunger contacts connected to the printed circuit board. The plunger contacts extend into the cradle area in the charger where the cell phone is placed. The plunger contacts are positioned in the cradle area to align with mating contacts on the cell phone when the cell phone is inserted into the cradle area. 
     The typical electrical connector of the foregoing type includes a rectangular housing with a mating face opposite an open side of the housing. The housing carries cylindrical casings that are open at one end along the mating face and that have closed contact bases at an opposite end along the open side of the housing. The closed contact bases are connected to the printed circuit board. The casings retain springs and cylindrical or bullet shaped contacts with the springs positioned between an end of the bullet contacts and contact bases. An opposite end of the bullet contacts extends partially through the open ends of the casings at the mating face of the housing. When a cell phone is mounted to the mating face, the bullet contacts engage mating contacts on the cell phone to join its battery. The bullet contacts are pushed downward into the casings, thereby compressing the springs. Thus an electrical path is formed that extends from the battery to the printed circuit board successively through the mating contacts on the cell phone to the bullet contacts, the springs, and the contact bases in the charger. 
     However, the typical electrical connector of the above noted type suffers from certain drawbacks. First, the cylindrical bodies of the bullet contacts are manufactured by a screw-machining process which is expensive and time-consuming because each bullet contact is machined from pre-existing metal stock. Secondly, the electrical connectors are time-consuming and expensive to assemble because each spring and bullet contact is separately loaded into a casing, and then the casings are loaded into the housing. Finally, the electrical path through the electrical connector is extensive. An electrical current travels from the bullet contact through the coils of the spring before reaching the contact base. The electrical current may pass through the length of the spring directly along the coils or, if the spring is completely compressed and the coils are contacting each other, from coil to coil. Because either such electrical path through the spring is extensive, an electrical current traveling through the spring encounters resistance. To overcome the resistance of the electrical path, more power is required to maintain an adequate supply of electrical current between the battery and the printed circuit board. 
     Therefore, a need exists for an electrical connector that overcomes the above problems and addresses other concerns experienced in the prior art. 
     BRIEF SUMMARY OF THE INVENTION 
     Certain embodiments provide for an electrical connector including a housing having a contact retention chamber and first and second mating faces configured to engage mating contacts. The electrical connector includes a cap having a first end configured to engage a mating contact and a second end being open. The electrical connector includes a plunger contact having a first end projecting from the housing. The first end is configured to engage a mating contact. The plunger contact has a second end that includes a spring retention area and that telescopically communicates with the cap. The plunger contact and the cap move relative to one another along a contact motion axis. The electrical connector includes a spring provided between the plunger contact and the cap that engages the spring retention area of the plunger contact along a contact/spring interface. At least one of the plunger contact and cap define the contact/spring interface to have an angled interface that biases the spring at an acute angle to the contact motion axis in order to induce a lateral binding force between the plunger contact and the cap. The lateral binding force causes the plunger contact and the cap to maintain a direct electrical connection therebetween independent of the spring during movement along the contact motion axis. 
    
    
     BRIEF DESCRIPTION OF SEVERAL VIEWS OF THE DRAWINGS 
     FIG. 1 illustrates a side isometric view of an electrical connector formed according to an embodiment of the present invention. 
     FIG. 2 illustrates an isometric section view of the electrical connector of FIG. 1 taken along section  2 — 2  of FIG.  1 . 
     FIG. 3 illustrates a side isometric view of a plunger contact formed according to an embodiment of the present invention. 
     FIG. 4 illustrates a front view of a cap formed according to an embodiment of the present invention. 
     FIG. 5 illustrates a side view of a portion of a beam formed according to an embodiment of the present invention. 
    
    
     The foregoing summary, as well as the following detailed description of certain embodiments of the present invention, will be better understood when read in conjunction with the appended drawings. For the purpose of illustrating the invention, there is shown in the drawings, certain embodiments. It should be understood, however, that the present invention is not limited to the arrangements and instrumentality shown in the attached drawings. 
     DETAILED DESCRIPTION OF THE INVENTION 
     FIG. 1 illustrates a side isometric view of an electrical connector  10  formed according to an embodiment of the present invention. The electrical connector  10  includes an insulative housing  14  having a rectangular mating face  18  that engages an electronic component such as a battery (not shown) and a mounting side  22  that is secured to a printed circuit board (not shown) along support legs  20 . The housing  14  retains plunger contacts  26  each having a rounded plunger portion  30  that extends through a respective aperture  34  in the mating face  18  of the housing  14  for engagement with the battery. Rectangular contact plates  38  corresponding to the plunger contacts  26  are disposed on the mounting side  22  of the housing  14  for engagement with conductive contacts (not shown) on the printed circuit board. The term contact is used broadly and includes pads formed on the printed circuit board at ends of electrical traces. Thus, the electrical connector  10  electrically interconnects the battery with the printed circuit board. 
     FIG. 2 illustrates an isometric section view of the electrical connector  10  of FIG. 1 taken along section  2 — 2  of FIG.  1 . The housing  14  includes a contact retention chamber  42  that is divided into contact compartments  46  by interior walls  44  that may include curved partitions  50 . Each contact compartment  46  retains a plunger contact  26 , a cap  54 , and a spring  58 . Each contact compartment  46  is aligned with a corresponding aperture  34  in the mating face  18  such that when the plunger contacts  26  are inserted into the contact compartments  46 , the plunger portions  30  of the plunger contacts  26  extend through the apertures  34 . The partitions  50  are configured to closely surround each spring  58  and each plunger contact  26 , thereby stabilizing each spring  58  and guiding each plunger contact  26  for movement along an associated contact motion axis  62  as the plunger contact  26  is depressed against the spring  58  in the direction of arrow A. 
     FIG. 3 illustrates a side isometric view of the plunger contact  26 . The plunger contact  26  has a tuning fork shape that is stamped from an electrically-conductive material without any other particular forming steps. The plunger contact  26  includes the plunger portion  30  extending from one end of an intermediate portion  86  and legs  66  extending from an opposite end of the intermediate portion  86 . The legs  66  have exterior surfaces  90  that face outward from one another. A spring abutment surface  70  extends along the end of the intermediate portion  86  between the legs  66  to define a spring retention area  74 . The spring abutment surface  70  is formed at an acute angle with respect to the contact motion axis  62  of FIG.  2 . The spring retention area  74  receives a first end of the spring  58  (FIG. 2) as the spring  58  engages the spring abutment surface  70 , and the legs  66  move telescopically within the cap  54 . 
     FIG. 4 illustrates a front view of the cap  54 . The cap  54  is stamped from a single piece of electrically-conductive material into a U-shape. The cap  54  includes the contact plate  38  with beams  38  extending upward from opposite ends thereof parallel to one another. The beams  78  have interior surfaces  94  and exterior surfaces  98 . As better shown in FIG. 5, barbs  82  extend transversely from sides  79  of the beams  78  and are dimensioned to form an interference-fit between the partitions  50  of the housing  14  (FIG.  2 ). Alternatively, the cap  54  may not be planar, but instead may be another shape such as circular, tubular, or cup-shaped. Optionally, the partitions  50  may be correspondingly dimensioned to receive the cap  54  in such other shapes to form an interference fit therebetween. 
     Returning to FIG. 2, during assembly the plunger contacts  26  are attached to a carrier strip (not shown) which is used to insert the plunger contacts  26  through the mounting side  22  of the housing  14  in the direction of arrow B into the contact compartments  46  until the plunger portions  30  extend upward through corresponding apertures  34 . The carrier strip is then cut away from the plunger contacts  26  and the springs  58  are inserted upward in the direction of arrow B into the contact compartments  46  until being located within the spring retention areas  74  of the plunger contacts  26 . The caps  54  then are inserted into the corresponding contact compartments  46  until the beams  78  are positioned between the partitions  50  and the interior walls  44  of the housing  14 . The barbs  82  on the beams  78  (FIGS. 4 and 5) engage the partitions  50  to retain the caps  54  in place, which in turn holds the springs  58 , and the plunger contacts  26  in the contact compartments  46 . 
     Top coils  88  of the springs  58  are positioned between the legs  66  of the plunger contacts  26  and engage and support the plunger contacts  26  along the spring abutment surfaces  70 . The legs  66  in turn are positioned between the beams  78  of the caps  54 . The contact plates  38  of the caps  54  may then be soldered to the printed circuit board. 
     In operation, the mating contacts of an electronic component, such as a cell phone battery are positioned on the mating face  18  until electrically engaging corresponding plunger portions  30 . The weight of the electronic component causes the plunger portions  30  to move downward in the direction of arrow A such that the springs  58  are compressed between the spring abutment surfaces  70  and the contact plates  38 . The legs  66  of the plunger contacts  26  contemporaneously move downward in the direction of arrow A relative to the beams  78  along the contact motion axis  62 . Because the spring abutment surfaces  70  are aligned at an acute angle to the contact motion axis  62 , the plunger contacts  26  experience a pivot force in the direction of arrow C. As the plunger contacts  26  pivot, the exterior surfaces  90  of the legs  66  on the plunger contact  26  engage the interior surfaces  94  of the beams  78  on the cap  54  thereby creating an electrical path between the battery and the printed circuit board. The spring abutment surfaces  70  and the springs  58  thus interact to induce a lateral binding force between the plunger contacts  26  and the caps  54  that forms a direct electrical connection between the plunger contacts  26  and the caps  54 . As the plunger contacts  26  are further depressed downward-in the direction of arrow A, the exterior surfaces  90  and interior surfaces  94  maintain contact through telescopic motion by slidably engaging each other. 
     Alternatively, when the electronic component is removed from the mating face  18 , the plunger contacts  26  are deflected upward in the direction of arrow B by the springs  58 . The legs  66  of the plunger contacts  26  disengage from the beams  78  of the caps  54  and return to an unbiased position resting upon the springs  58  with the plunger portions  30  extending through the apertures  34  of the mating face  18 . 
     In an alternative embodiment of the electrical connector  10 , the angled spring abutment surface  70  is located on an interior side of the contact plate  38  of the cap  54  and engages a second end of the spring  58 . Thus the lateral binding force is created along the contact plate  38  of the cap  54  as the plunger contact  26  pushes the spring  58  downward in the direction of arrow A against the spring abutment surface  70 . Optionally, the legs  66  of the plunger contact  26  may telescopically enclose the beams  78  of the cap  54  within the spring retention area  74  such that interior surfaces of the legs  66  contact the exterior surfaces  98  of the beams  78  to create the lateral binding force. In another embodiment, only one leg  66  of the plunger contact  26  engages a proximate beam  78  of the cap  54  when the spring abutment surface  70  compresses and pivots about the spring  58 . Thus the electrical path extends through only the engaged leg  66  and beam  78 . 
     The electrical connector confers several benefits. First, the electrical connector creates a direct electrical path from the plunger contact to the cap that is shorter than an electrical path from the plunger contact to the cap via the spring. Because the electrical path is shorter, the electrical current experiences less resistance, and thus less power is necessary to electrically connect the battery with the printed circuit board. Secondly, the plunger contacts and caps are planar and may be easily stamped from metal sheets without and molding or machining. Thus, the electrical connector is inexpensive and efficient to manufacture. Finally, the electrical connector is quickly and efficiently assembled entirely within the housing by successively inserting the plunger contacts, springs, and caps. 
     While the invention has been described with reference to certain embodiments, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted without departing from the scope of the invention. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the invention without departing from its scope. Therefore, it is intended that the invention not be limited to the particular embodiment disclosed, but that the invention will include all embodiments falling within the scope of the appended claims.