PATENT DOCUMENT

Publication Number: US-8882529-B2
Application Number: US-201213607600-A
Country: US
Kind Code: B2

Title: Latch assembly having spring arms each with a retaining portion and a reinforced portion

Abstract:
A retention latch mechanism having a retention spring of a first connector engageable with a retention feature of a second connector. The retention spring may include a spring arm having a distal, curved retaining portion that is resiliently received within the retention feature and a reinforced portion that is proximal of the distal retaining portion. The reinforced portion includes a layer having residual compressive stress to inhibit fatigue failure during repeated cycling of the latch mechanism. The reinforced portion may be formed by a cold working method, such as shot peening a select region of the spring arm. The reinforced portion is formed to inhibit fatigue failure during repeated cycling of the latch mechanism. Methods of forming a retention mechanism having a retention spring with a reinforced portion are provided herein.

Claims:
What is claimed is: 
     
       1. A method of fabricating a retention latch assembly for retaining a plug connector releasably coupled within a receptacle connector of a device in a mated configuration, the method comprising:
 providing one or more retention spring arms for placement within the receptacle, each retention spring arm comprising a distal retaining portion that curves inwardly toward an insertion axis along which the plug connector is inserted into the receptacle and is configured to engage a corresponding retention feature of the plug connector when the plug connector is coupled with the receptacle connector; and 
 creating a reinforced portion in each of the one or more retention spring arms at a select location entirely proximal of the distal retaining portion by forming a compressive residual stress layer therein. 
 
     
     
       2. The method of  claim 1 , wherein forming the compressive residual stress layer comprises shot peening the one or more spring arms at the select location. 
     
     
       3. The method of  claim 1 , wherein the compressive residual stress is greater than 1,000 MPa. 
     
     
       4. The method of  claim 2 , wherein shot peening comprises a WPC treatment. 
     
     
       5. The method of  claim 2 , wherein shot peening is performed with beads of glass, ceramic or metal. 
     
     
       6. The method of  claim 5 , wherein the beads are between 50-150 microns. 
     
     
       7. The method of  claim 6 , wherein the beads are shot at a pressure between 25 and 125 psi. 
     
     
       8. The method of  claim 7 , wherein the beads are shot at the select location at a pressure between 50 psi and 100 psi. 
     
     
       9. The method of  claim 5 , wherein the beads are shot at the select location from a plurality of angles about the select location of the spring arm so that the layer of residual compressive stress substantially circumscribes the spring arm at the select location. 
     
     
       10. The method of  claim 5 , wherein the select location is an area at which a maximum stress occurs during a maximum displacement of the spring arm during a cycle of use. 
     
     
       11. The method of  claim 5 , wherein the select location includes a transition area at which a vertical width of the respective spring arm narrows. 
     
     
       12. The method of  claim 2 , wherein the select location includes less than 30% of the outer surface of the entire spring arm. 
     
     
       13. The method of  claim 9 , wherein the one or more retention spring arms comprise a pair of resilient spring arms, each spring arm extending distally from a proximal base to the distal retaining portion of the respective spring arm, wherein the beads are shot at the select location so that the compressive residual stress layer extends to a depth of about 5 to 10 μm below the surface of the select portion. 
     
     
       14. The method of  claim 13 , wherein the select location includes a shouldered transition area of the spring arm at which a vertical width of the spring arm narrows, the transition area being located about midway between the proximal base and the distal retaining portion on each respective arm. 
     
     
       15. The method of  claim 14 , wherein the select portion extends a length of about 2-5 mm along a direction of the insertion axis.

Description:
CROSS-REFERENCES TO RELATED APPLICATIONS 
     This application is a non-provisional of and claims priority to U.S. Provisional Application No. 61/693,232 filed on Aug. 24, 2012, the entire contents of which are incorporated herein by reference. 
    
    
     BACKGROUND OF THE INVENTION 
     The invention relates generally to retention mechanisms, and in particular retention mechanisms for use in electrical connectors. 
     Many devices include electrical connectors to facilitate communication between devices and/or recharging of the device by electrically coupling the device to an external power source. In a typical electrical connector system an electrical connection can be made between a plug connector and a corresponding receptacle connector by inserting the plug connector into the corresponding receptacle connector. Generally, the plug connector includes a group of electrical contacts that engage and electrically couple with corresponding electrical contacts within the receptacle connector when connected. To ensure proper contact is maintained between corresponding contacts, some electrical connectors include interfacing features or retaining features that engage to retain the connector plug within the receptacle connector. These interfacing surfaces or retention mechanisms or features may encounter wear-and-tear during use and experience fatigue failure after many cycles of use. 
     BRIEF SUMMARY OF THE INVENTION 
     Various embodiments of the invention pertain to a retention mechanism having increased fatigue strength, such as may be used in electrical connectors, that improves upon some or all of the above described deficiencies. Other embodiments of the invention pertain to methods of manufacturing electronic connectors as well as electronic devices that include such connectors having retention mechanisms. 
     In view of the shortcomings of some currently available electronic connectors described above, embodiments of the invention relate to connectors with improved retention mechanisms that provide retention forces between an electrical connector plug and a connector receptacle. The retention mechanism may provide an increased normal force between the electrical contacts of the electrical connector plug and the receptacle and improved ease of use by providing a more consistent feel when a connector plug is inserted and extracted from the receptacle. The mechanism includes a retention spring on a first connector, the retention spring having a retaining portion that interfaces and engages with a retention feature of a second connector, the retaining portion and the retention feature being engaged with the first and second connector when mated. In some embodiments, the mechanism includes a retention spring with a distal retaining portion and a proximal reinforced portion having a layer of compressive residual stress so as to inhibit fatigue failure of the proximal portion after many cycles of use. The compressive residual stress layer may be formed by a cold working process, such as shot peening, particularly a wide peening and cleaning (WPC) treatment. A WPC treatment uses relatively small particles of shot and may be used as a surface enhancement to reduce friction by smoothing a surface. When utilized on a select portion of a retention spring, as described herein, the compressive residual stress layer near the surface inhibits the formation of stress fractures, thereby improving the fatigue strength of the retention spring and prolonging the useful life of the component. Formation of a compressive residual stress layer over the entire retention spring is not required and improvement of the retention spring can be obtained by treatment of a select portion of the retention spring, such as a portion proximal of a retaining portion near a narrowing or shoulder region of the retention spring where a stress fracture may form after many cycles of use. 
     Although various aspects and features of the invention are described in relation to electrical connectors depicted in the accompanying figures, it is appreciated that these features and aspects can be used in a variety of different applications and different connector devices, and that the invention is not limited to the exemplary connectors described herein. 
     In one aspect, the invention pertains to a retention latch mechanism for use in an electrical connector device having an electrical connector plug and a corresponding receptacle. In some embodiments of the invention, electrical contacts are formed an at least one surface of the connector plug and arranged in a symmetrical layout so that the contacts align with contacts of the connector receptacle. When the connector plug is fully inserted into the receptacle into a mated configuration, the individual contacts on the connector plug are electrically coupled to the corresponding electrical contacts within the receptacle and a retention mechanism provides a retention force to maintain the electrical coupling between the connector plug and the receptacle. 
     Methods of creating a retention mechanism include: forming a retention spring having a distal, retaining portion and a proximal reinforced portion having a layer with residual compressive stresses. The proximal reinforced portion may be created by cold working methods, such as shot peening, as in any of the methods described herein. 
     To better understand the nature and advantages of the invention, reference should be made to the following description and the accompanying figures. It is to be understood, however, that each of the figures is provided for the purpose of illustration only and is not intended as a definition of the limits of the scope of the invention. In general, and unless it is evident to the contrary from the description, where elements in different figures use identical reference numbers, the elements are either identical or at least similar in function. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  shows an electrical connector device, in accordance with embodiments of the invention. 
         FIGS. 2A-2B  illustrate an example electrical connector device. 
         FIGS. 3A-3B  show an example connector plug and receptacle an electrical connector device, in accordance with some embodiments. 
         FIG. 3C  shows an example connector plug. 
         FIG. 4  shows an insertion and extraction performance profile relating to an example electrical connector device. 
         FIGS. 5A-5B  depict the contact forces and stresses associated with use of an example electrical connector device. 
         FIGS. 6A-6B  depict the locations of contact forces and stresses seen in testing of an example retention device. 
         FIGS. 7A-7C  illustrate sequential cross-sections along an insertion plane showing the insertion of a connector plug into a connector receptacle in an example connector. 
         FIG. 8  shows an example pair of retention springs. 
         FIGS. 9A-9B  illustrate cross-sectional views of a proximal portion of the retention spring before and after treatment in an example connector receptacle. 
         FIGS. 10A-10B  show an example retention spring and supporting metal tab from which the spring is formed and a detail view of one of a pair of springs in the example retention spring, respectively. 
         FIG. 11  shows an example method. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     The invention will now be described in detail with reference to certain embodiments thereof as illustrated in the accompanying drawings. In the following description, numerous specific details are set forth in order to provide a thorough understanding of the invention. It will be apparent, however, to one skilled in the art, that the invention may be practiced without some or all of these specific details. In other instances, well known details have not been described in detail in order not to unnecessarily obscure the concepts and principles of the invention. 
     In order to better appreciate and understand the invention, reference is first made to  FIG. 1  which is a simplified schematic representation of connector device  100  having a retention latch mechanism according to an embodiment of the invention. The connector device  100  includes a connector plug  10  insertable into the corresponding connector receptacle  20 . The external contact connector plug  10  includes multiple electrical contacts  12  that can accommodate some or all of video, audio, data and control signals along with power and ground. Connector plug connector plug  44  is compatible with a connector receptacle  20  of a host device  200  that can be, for example, a portable media player. Each of the connector plug  10  and the connector receptacle includes retention features  14 ,  24 , respectively, that engage when the connector plug  10  is fully inserted within the receptacle  20  in a mated configuration, so as to aid in the alignment and electrical contact between the components and maintain the components in the mated configuration. 
       FIGS. 2A-2B  illustrate an example electrical connector plug  10  before and after insertion into a compatible connector receptacle  20 , respectively. As shown in  FIG. 2A , the electrical connector  10  includes a connector plug  44  having electrical contact region  46  with a plurality of electrical contacts  12  for electrically coupling to corresponding electrical contacts (not shown) disposed inside the receptacle  20 . The connector receptacle  20  is generally defined by an outer receptacle housing  30  that is attached to a surface or components on the interior of device  200 , such as by use of one or more brackets  32 ,  34 . In the embodiment shown, the connector receptacle housing  30  is coupled within the device using an upper bracket  32  that extends over the upper portion of the housing  30  and a lower bracket  34  that extends underneath housing  30 . The end portions of each bracket  32  and  34  include holes for receiving a screw to facilitate mechanically coupling the housing  30  within the device  200 . The connector plug  10  and connector receptacle are connected by inserting the connector plug  44  along insertion axis x until the connector plug  44  is fully inserted into a mated configuration in which corresponding electrical contacts  12 ,  22  are electrically coupled, as shown in  FIG. 2B . 
       FIGS. 3A-3C  illustrate the connector plug  44  of the plug  10  and the connector receptacle  14  of  FIGS. 2A-2B  in further detail.  FIG. 3A  depicts the connector plug  10  having the insertable connector plug  44 . Connector plug  10  includes a connector plug body  42  and the connector plug portion  44  that extends longitudinally away from body  42  in a direction parallel to the length of the connector plug  10 . A cable  43  can optionally be attached to body  42  at an end opposite of connector plug portion  44 . Body  42  is shown transparent form so that certain internal components are visible. As shown, within body  42  is a circuit board insert, such as a printed circuit board (PCB),  104  that extends into ground ring  105  between contact regions  46  and  46  towards the distal tip of connector plug  10 . One or more integrated circuits (ICs), such as Application Specific Integrated Circuit (ASIC) chips  108   a  and  108   b , can be operatively coupled to the circuit board insert  104  to provide information regarding connector plug  10  and any accessory or device that connector plug  10  is part of and/or to perform specific functions, such as authentication, identification, contact configuration and current or power regulation. 
     In the above embodiment, connector plug  44  is sized to be inserted into a corresponding connector receptacle  20  during a mating event and includes a first contact region  46  formed on a first major surface  44   a  extending from a distal tip of the connector plug to a spine  109  such that when connector plug  44  is inserted into the connector receptacle, the spline abuts a housing  30  of the connector receptacle or host device in which the connector receptacle resides. In one particular embodiment, connector plug  44  is 6.6 mm wide, 1.5 mm thick and has an insertion depth (the distance from the tip of connector plug  44  to spine  109 ) of 7.9 mm. Connector plug  44  may be made from a variety of materials including metal, dielectric or a combination thereof. For example, connector plug  44  may be a ceramic base that has contacts printed directly on its outer surfaces or may include a frame made from an elastomeric material that includes flex circuits attached to the frame. In some embodiments, connector plug  44  includes an exterior frame made primarily or exclusively from a metal, such as stainless steel, with a contact region  46  formed within an opening of the frame. The structure and shape of connector plug  44  may be defined by a ground ring  105  and made from stainless steel or another hard conductive material. 
     In this embodiment, contact region  46  is centered between the opposing side surfaces  44   c  and  44   d , and a plurality of external contacts are shown formed on the top outer surface of connector plug  44  within the contact region. The contacts can be raised, recessed or flush with the external surface of connector plug  44  and positioned within the contact region such that when connector plug  44  is inserted into a corresponding connector receptacle they can be electrically coupled to corresponding contacts in the connector receptacle. The contacts can be made from copper, nickel, brass, stainless steel, a metal alloy or any other appropriate conductive material or combination of conductive materials. In some embodiments, contacts are printed on surfaces  44   a  using techniques similar to those used to print contacts on printed circuit boards. The contacts can be stamped from a lead frame, positioned within regions  46  and surrounded by dielectric material. 
     In one aspect, the connector plug  44  includes one or more retention features  14  corresponding to one or more retention features  24  within the receptacle  20 . For example, the retention features of the connector plug  44  may include one or more indentations, recesses, or notches  14  on each side of connector plug  44  that engage with corresponding retention feature(s)  24  within the receptacle, the corresponding retention feature(s)  24  extending or protruding toward the insertion axis along which the connector plug  44  is inserted so as to be resiliently received within the indentation, notch or recess within the sides of connector plug  44 . In one particular embodiment, retention features  14  are formed as curved pockets or recesses in each of opposing side surfaces  44   c ,  44   d , the shape and location of the retention features  14  corresponding to complementary retention features  24  in the receptacle when in a mated configuration. Generally, the retention features  24  of the receptacle resemble spring-like arms configured to be resiliently received within retention feature recesses  14  once the connector plug  10  and receptacle  20  are properly aligned and mated. The engagement of these resilient retention features of the receptacle and the retention feature within the connector plug can be seen in more detail in  FIG. 3C . The length of each spring-like arm extends about 8-10 mm along the insertion axis so as to retain the connector plug when fully inserted within the receptacle at an insertion depth of about 7.9 mm. 
     In some embodiments, one or more ground contacts are formed on connector plug  44 , or may be included on an outer portion of connector plug  44 . In some embodiments, the one or more ground contacts are formed within and/or as part of a pocket, indentation, notch or similar recessed region  14  formed on each of the side surfaces  44   c ,  44   d  (not shown in  FIG. 3   a ), such that the retention feature  14  may also act as the electrical ground for connector plug  44 . 
       FIG. 3B  depicts a connector receptacle  20  in accordance with some embodiments. The connector receptacle  20  also includes side retention mechanisms  24  that engage with corresponding retention features  14  on connector plug  10  to secure connector plug  10  within cavity  147  once the connectors are mated. In some embodiments, the retention mechanisms  24  are resilient members or springs, often formed from an elongated arm that extends from a rear portion of the receptacle and extends toward the opening of cavity  147 , such as shown in more detail in  FIG. 3C . The retention mechanisms  24  may be made from an electrically conductive material, such as stainless steel, so that the feature can also function as a ground contact. The connector receptacle  20  can also include two contacts  28 ( 1 ) and  28 ( 2 ) that are positioned slightly behind the row of signal contacts and can be used to detect when connector plug  10  is inserted within cavity  140  and/or when connector plug  10  exits the cavity  147 . When connector plug  44  of connector plug  10  is fully inserted within cavity  147  of connector receptacle  20  during mating between the connector plug and connector receptacles, each of contacts  12 ( 1 ) . . .  12 ( 8 ) from one of contact region  46  are physically coupled to one of contacts  22 ( 1 ) . . .  22 ( 8 ). 
     In this embodiment, body  42  of connector plug  10  is generally the portion of connector  40  that a user will hold onto when inserting or removing connector  40  from a corresponding connector receptacle. Body  42  can be made out of a variety of materials and in some embodiments is made from a dielectric material, such as a thermoplastic polymer formed in an injection molding process. While not shown in  FIGS. 3A  or  3 B, a portion of cable  43  and a portion of connector plug  44  may extend within and be enclosed by body  42 . Electrical contact to the contacts in contact region  46  can be made to individual wires in cable  43  within body  42 . Cable  43  may include a plurality of individual insulated wires, one for each electrically unique contact within regions  46  and  46 , that are soldered to bonding pads on a circuit board insert housed within body  42 . Each bonding pad on the circuit board insert is electrically coupled to a corresponding individual contact within one of contact region  46 . Also, one or more integrated circuits (ICs) can be operatively coupled within body  42  to the contacts within regions  46  to provide information regarding connector  40  and/or an accessory the connector is part of or to perform other specific functions as described in detail below. 
     In one aspect, body  42  may be fabricated in any of variety of suitable shapes, including a circular cross section, an oval cross section, or a rectangular cross-section. In some embodiments, such as shown in  FIG. 3A , body  42  has a rectangular cross section with rounded or angled edges (referred to herein as a “generally rectangular” cross section), that generally matches in shape but is slightly larger than the cross section of connector plug  44 . In some embodiments, both the body  42  and connector plug  44  of connector  10  have the same cross-sectional shape and have the same width and height (thickness). As one example, body  42  and connector plug  44  may combine to form a substantially flat, uniform connector where the body and connector plug seem as one. In still other embodiments, the cross section of body  42  has a different shape than the cross section of connector plug  44 , for example, body  42  may have curved upper and lower and/or curved side surfaces while connector plug  44  is substantially flat. 
       FIG. 3C  depicts the connector plug  44  of the connector plug  10  fully inserted into the connector receptacle  20  (the receptacle housing  30  is shown as transparent so that certain internal components are visible). As can be seen, when the connector plug  44  is fully inserted into the receptacle  20 , the electrical contacts  22  engage with and electrically couple with the group of electrical contacts  12  on the top surface of the connector plug  10 . Also, when the connector plug  44  is fully inserted and properly positioned within the receptacle  20  in the mated configuration, the corresponding retention features on each of the components are engaged, which helps ensure proper alignment of the components as well as retaining the connector plug  10  within the receptacle  20 , as shown in  FIG. 3C . As in some embodiments, the retention features  24  of the receptacle  20  are two spring-like resilient arms  24  that extend from base  27  at a rear portion of the receptacle housing  30  along each side of the receptacle housing  30  toward a distal retaining portion  25  near the opening of the cavity in which connector plug  44  is inserted. A portion of the spring arm  24  proximal of the retaining portion  25  is treated to create a reinforced portion  26  having a residual compressive stress layer, such as may be created by shot-peening an outer surface of the treated portion  26 . Although in some embodiments, the entire spring arm  24  may be treated, improved fatigue strength of the mechanism can be obtained by treating a relatively small portion of the spring arm  24  that experiences the maximum stresses during cycling. The treated reinforced portion  26  may be less than 30% of the outer surface of the spring arm  24 , such as about 25% or less than 10% of the outer surface of each retention spring-arm  24 . 
     As shown in  FIGS. 3A-3C , the first and second retention features  410  may be formed on the opposing sides of connector plug  44  within ground ring  105  and are adapted to engage with one or more corresponding features within the connector receptacle  20  to secure the connectors together when mated. Often, the retention features  14  are semi-circular indentations in the side surfaces of connector plug  44 . The retention features may be widely varied and may include angled indentations or notches, pockets that are formed only at the side surfaces and do not extend to the top surface  44  or opposing bottom surface. The resilient spring arm retention features  24  of the receptacle  20  may include a tip or an angled or curved surface retaining portion  25  (such as the inwardly curved portion shown in  FIGS. 3A-3C ) that slides into and fits within the recessed retention features  14  of the connector plug  10 . 
     In some embodiments, the retention features  24  of the receptacle are designed so that the curved retaining portion  25  that engages with the corresponding retention features  14  of the plug  10  is positioned near the opening of the cavity in which connector plug  44  is inserted. This may help better secure the connector sideways when it is in an engaged position within the connector receptacle. It is appreciated however, that either of the retention features could be located or positioned in any suitable location so that when engaged the retention features help retain the components in the proper alignment in the mated configuration. 
     In an example embodiment, the angled and curved surfaces of corresponding retention features of the connector plug  44  and the connector receptacle  120  are configured so as to provide a desired insertion force and extraction force, such as the forces depicted in the insertion/extraction force profile shown in  FIG. 4 . The retention features of each of the connector plug and the connector receptacle can be designed or modified, such as by increasing or decreasing the curvature of one or both features or by changing the spring force exerted by the resilient arm, so as to provide desired insertion and extraction forces. In some embodiments, the force required to extract the connector plug  44  from the receptacle  120  is greater than the force required to insert the connector plug  44  into the receptacle  120 . This aspect increases ease of use by allowing a user to easily insert the connector plug  44  of the connector plug  10  into the receptacle  120 , and recognize when the connector plug  44  is properly positioned due to the tactile response resulting from engagement of the corresponding retention features, and further prevents inadvertent or accidental withdrawal of the connector plug  10  from the receptacle  120 . As described above, in embodiments utilizing features similar to those in  FIGS. 3A-3C , the insertion and extraction forces may vary according to a variety of factors that may include the angle or curvature of the recess and/or the corresponding resilient arm, as well as the material and width of the resilient arm itself. 
     While the retention features described above offer significant advantages in some connector designs, these features may present additional challenges. For example, in an embodiment where the receptacle includes retention features comprising a pair of resilient arms extending on opposite sides of the receptacle, the lateral movement of the resilient arms while the connector plug is being inserted may result in substantial contact forces and stresses within the resilient arms or springs. Repeated cycling of these stresses and contact forces over many cycles of use may ultimately cause material failure or fatigue failure, resulting in cracking or breaking of the resilient arm. An example of typical contact forces and stresses associated with insertion and retraction of some connector devices using retention features similar to those described above is shown in  FIGS. 5A-5B . As can be seen in  FIG. 5A , in some connector devices, the contact forces can cause lateral deflection of a resilient arm retention feature to exceed a maximum allowable deflection, which would result in material failure. 
     Examples of material properties associated with materials commonly used in connector assemblies in accordance with some embodiments are presented in Table 1 below. In an example embodiment, 301 ¾ h Stainless Steel is used for the spring arms retention features due to its high stiffness and forming ability. In an untreated retention spring, material failure was noted after cycles of use ranging from 2,000 to 7,000 cycles. By treating a proximal portion of the retention spring to create a proximal reinforced portion having a layer of residual compressive stresses allows the retention spring, such as any of those described herein, to operate for over 10,000 cycles of use without material failure. Examples of the advantages in fatigue strength when using various methods of treatment to create a reinforced portion can be found in the experimental results depicted in  FIGS. 10A-10D  and  FIGS. 12A-12C . 
     
       
         
           
               
             
               
                 TABLE 1 
               
             
            
               
                   
               
               
                 Material Properties for Selected Spring Arm Materials 
               
            
           
           
               
               
               
               
               
            
               
                   
                   
                 Tensile 
                 Yield 
                 Fatigue/Endurance 
               
               
                   
                 E 
                 Strength 
                 Strength 
                 Limit 
               
               
                   
                   
               
            
           
           
               
               
               
               
               
               
               
            
               
                 301¾ 
                 h 
                 L-direction 
                 193 GPa 
                 1250 MPa 
                 950 MPa 
                 850 MPa 
               
               
                 301¾ 
                 h 
                 C-direction 
                 193 GPa 
                 1180 MPa 
                 850 MPa 
                 750 MPa 
               
               
                 301 
                 h 
                 L-direction 
                 193 GPa 
                 1400 MPa 
                 1250 MPa  
                 1000 MPa  
               
               
                 301 
                 h 
                 C-direction 
                 193 GPa 
                 no data 
                 no data 
                 850 MPa 
               
               
                   
               
            
           
         
       
     
     Examples of forces and stresses experienced by a spring-arm retention spring are illustrated in the stress models shown in  FIGS. 6A-6B . Although the strength of the material can be modified by using a thicker or different material, generally such modifications affect the flexibility of the arm, which may result in an undesirable insertion/extraction profile. In some connector designs, the lateral outward displacement of the resilient arm retention feature may cause the resilient arm to contact a portion of the receptacle housing or other such component, which further increases the force and stresses within the resilient arm making material failure more likely. 
     In some embodiments using the resilient spring arms described above, the receptacle may further include a stress reducing member, such as any of the backup springs described in U.S. Provisional Application 61/597,705 and 61/602,057, the entire contents of which are incorporated herein by reference. Such backup springs may be positioned adjacent the angled or curved retaining portion that is received within the corresponding recess of the tab, to directly counter the forces applied by the connector plug  44  during insertion, although in some embodiments, the backup spring may be placed in other locations, such as closer to a mid-point of the resilient arm or closer to a rear portion of the resilient arm. Generally, the stress reducing member is positioned adjacent a side or outer surface of the resilient arm which faces away from the insertion axis along which the connector plug is inserted into the receptacle cavity, to allow the inner surface of the resilient arm to contact connector plug during insertion and be received within the recess of the connector tab. As the one or more resilient arms are displaced laterally outward during insertion of the connector tab, the resilient arm(s) contact and press against the stress reducing resilient member which helps relieve some of the forces exerted against the resilient arm(s) by the connector plug and the stresses within. Although in some embodiments, the increased fatigue strength improves the fatigue strength sufficiently to obviate the need for a stress reducing member. 
     The use of a retention mechanism in accordance with an embodiment of the invention can be further understood by referring to  FIGS. 7A-7C , which sequentially illustrates the insertion of a connector plug into a receptacle having such a retention mechanism.  FIG. 7A  shows an embodiment of a connector having a retention mechanism shown prior to insertion of the connector plug  10  in receptacle  20 . As can be seen, the width of the front portion of the connector plug  44  (w 1 ) is wider than the distance between the curved retaining portions  25  of the resilient arms  24  (d 1 ) of the receptacle so that insertion of the connector plug  44  displaces the spring arms  24  laterally outward. It can also be seen that the width (w 2 ) between the recessed retention features  14  is greater than the distance d 1 , so that when the plug  10  and receptacle  20  are in the mated configuration, the retaining portions  25  of the spring arms  24  exert a force on the connector plug  44  toward the insertion axis x. 
       FIG. 7B  illustrates insertion of the leading portion of the connector plug  44  into the receptacle  20  between the spring arms  24 , which displaces each of the spring arms  24  laterally outward away from the insertion axis (x). In some embodiments, the maximum stress is experienced by the spring arm retention spring  24  occurs at a proximal region during the maximum outward displacement of the spring arms, which is the region that is treated to create the reinforced portion  26 . To inhibit stress fractures, treated reinforced portion  26  has been treated by a WPC treatment to provide a layer near the surface having residual compressive stresses. In some embodiments, region  26  is a transition area of the retention spring  24 , the transition area having a narrowed region or shoulder. 
       FIG. 7C  illustrates the connector plug  10  fully inserted within the receptacle  20  within the mated configuration, each of the electrical contacts  12  of the connector plug  10  electrically coupled with the electrical contacts  22  of the receptacle  20 . As can be seen, the curved retaining portions  25  of the spring arm retention features  24  are engaged within the recessed retention features  14  of the connector plug  10  and the distance between the spring arms is w 2 , such that the spring arms are outwardly displaced in the mated configuration so as to provide a retaining force against the sides of the connector plug  44  as well as to ensure electrical contact so that the springs arms may function as a ground path for the ground ring of the connector plug  10 . 
       FIG. 8  depicts a pair of retention springs, such as may be used in a retention mechanism as described in  FIGS. 7A-7C . The pair of retention springs  24  may remain on a T-shaped bar of metal  29  from which the retention mechanism is formed to facilitate treatment with a shot peening method, such as a WPC treatment, the retention springs  24  being supported sufficiently on metal bar  29  so as to withstand the forces associated with shot peening. In a typical shot peening method small beads are shot at a surface in a controlled manner to create a layer of residual stresses beneath the treated surface. Treatment may use glass beads, a hard ceramic (e.g. silicon nitride), or metal beads (e.g. iron or steel beads). The beads may be anywhere from 1 to 200 microns, often about 100 microns and are shot at sufficient power to compress the material, often within a range of pressures or powers (e.g. low, medium or high power). Generally, low power is about 50 psi, medium power is about 100 psi and high power is about 150 psi, although it is appreciated that power may be varied within a given range if desired, such within +/−25 psi from the above noted powers. Generally, the entire outer surface of the treated area  26  is shot peened so that the surface is hit by the shot evenly from all outside angles. This may be accomplished by shot peening the treated zone from different sources disposed at different areas to hit the surface from various angles, such as two peening sources on one side of the retention spring to direct shot to an outer facing surface from two different angles and two sources adjacent the opposing side to direct shot to an inner facing surface of the reinforced portion  26 . 
     Although, the entire retention spring  24  may be treated, the above noted improvements in performance and fatigue strength can be obtained from treating a select portion of the retention spring  24  proximal of the curved retaining portion  25 , such as a select portion may be confined to an area that experiences the greatest stress during the maximum outward displacement of the spring-arm retention springs  24 . In an embodiment in which the spring-arm has a shoulder region that reduces in width near a mid-portion of the spring arm, as shown in  FIG. 8 , the select portion may be an area of at least a couple millimeters at the shoulder region, such as a region of about 2-4 millimeters roughly centered on the shoulder region so that the reinforced portion  26  extends about 2-4 millimeters in width along the insertion axis and circumscribes the spring arm so as to inhibit fatigue failure near the shouldered region. In a retention mechanism of a connector receptacle in which the connector plug has an insertion depth of about 8 mm, the reinforced portion  26  of the spring arm is located along a mid-portion of the spring arm proximal of an inwardly curved retaining feature  25 . In some embodiments, the reinforced portion is at a shouldered region on the spring arm, at which the vertical width of the spring arm reduces, disposed about 4 mm from the base of the retention mechanism from which each spring arm  24  extends. 
       FIGS. 9A-9B  shows a magnified view (×400) of a cross section of a surface of a treated zone  26  of the example retention spring  24  in  FIG. 8 , taken before and after treatment.  FIG. 9A  shows a cross-section before treatment, while  FIG. 9B  shows a cross-section taken after a shot peening treatment, specifically a WPC treatment, that created a layer having residual compressive stresses of at least 1500 MPa and extending to a depth of about 5 μm to 15 μm from the surface, such as a depth of about 10 μm from the surface. 
     Fatigue testing was conducted on various retention springs treated according to various differing shot peening methods by stressing the retention springs over many cycles of use. In some embodiments, the reinforced portion  26  is confined to an area of a spring arm  24  at which the width of the spring arm  24  narrows at a shoulder  26 , as shown in  FIG. 10B . The reinforced portion may include an area of at least a few millimeters at the narrowed, should region, such as an area about 2-10 millimeters wide. Each of the example retention springs  24  was cycled to simulate the stresses each would experience during normal use, as described in  FIGS. 7A-7C . 
     An example retention spring  24  without a treated area  26  experienced failure between 2 k and 7 k cycles of use (out of five samples of five experience fatigue failure). An example retention spring  24  that included a region  26  treated by a shot peen treatment using 100 micron iron beds at low shot power (about 50 psi) resulted in a retention spring that was able to endure 10 k cycles of use without experience fatigue failure (out of three samples, none failed). An example retention spring  24  that included a region  26  treated by a shot peen treatment as described above using 100 micron iron beds at medium shot power (about 100 psi) resulted in a retention spring that was able to endure 10 k cycles of use without experience fatigue failure (out of three samples, none failed). An example retention spring  24  that included a region  26  treated by a shot peen treatment as described above using 100 micron iron beds at high shot power (about 150 psi) resulted in retention springs  24  that failed at about 9 k cycles of use (two samples of four failed at about 9 k cycles of use). Thus, to provide improved fatigue strength, low and medium power shot peening is used in some embodiments. 
     An example of a retention spring is shown in  FIG. 10A , the retention spring pair is shown still attached to the metal bar  29  from which the retention spring is formed. The retention spring may remain attached to metal bar  29  to facilitate treatment of portion  26  as described herein. The retention spring includes a pair of retention springs  24  extending from a proximal base  27  to a distal inwardly curved retaining portion  25 . A proximal portion  26  has been treated to provide a layer having residual compressive stress to improve the fatigue strength of each retention spring. The pair of retention springs may be mounted on the T-shaped tab  29  to support the retention springs during the shot peening treatment. As can be seen in  FIG. 10B , the example retention spring arm  24  includes a transition area that narrows to a smaller width. Accumulation of stresses near the shoulder of this transition area can cause tiny stress fractures to occur that propagate and lead to fatigue failure within the transition area; thus, to improve fatigue strength, the retention spring can be treated in this transition area, such as by a shot peening or WPC treatment, to create reinforced portion  26 . 
     Additional fatigue failure testing was conducted on various retention springs treated according to three different shot peening methods: (Method A) glass beads shot at a low power, (Method B) metal beads shot at a medium power, and (Method C) metal beads shot at a higher power. Each of the example retention springs was cycled until fatigue failure occurred. The retention spring treated according to Method A experienced fatigue failure at 12 k cycles; the retention spring treated according to Method B experienced fatigue failure at 10 k cycles; and the retention spring treated according to Method C experienced fatigue failure at 10 k cycles. In each instance of fatigue failure, failure resulted from a stress fracture that originated inside the transition area at the shoulder. 
     Table 2, below, shows surface roughness measurements of the example retention spring in each of Methods A, B and C described above. As can be seen, Method A resulted in the smoothest surface, while Methods B and C resulted in an increasingly uneven surface, the higher shot peening power associated with the more uneven surface. 
     
       
         
           
               
             
               
                 TABLE 2 
               
             
            
               
                   
               
               
                 Surface Roughness of Tested Spring-Arms 
               
            
           
           
               
               
               
               
            
               
                   
                 Ra (μm) 
                 Ry (μm) 
                 Rz (μm) 
               
               
                   
                   
               
            
           
           
               
               
               
               
               
            
               
                   
                 A 
                 0.233 
                 1.605 
                 1.212 
               
               
                   
                 B 
                 0.369 
                 2.613 
                 2.116 
               
               
                   
                 C 
                 0.584 
                 4.178 
                 3.168 
               
               
                   
                   
               
            
           
         
       
     
     Table 3, below, illustrates the residual compressive stresses formed by each of the above noted methods in the treated zone (TZ) as well as in a treated area of the metal bar (for comparison purposes). 
     
       
         
           
               
             
               
                 TABLE 3 
               
             
            
               
                   
               
               
                 Residual Compressive Stresses 
               
            
           
           
               
               
               
            
               
                   
                 Metal Bar 
                 Treated Zone (TZ) 
               
               
                   
                   
               
            
           
           
               
               
               
            
               
                 A 
                 632 ± 157 MPa 
                 746 ± 243 MPa 
               
               
                 B 
                 409 ± 106 MPa 
                 362 ± 243 MPa 
               
               
                 C 
                  280 ± 60 MPa 
                 −26 ± 528 MPa 
               
               
                   
               
            
           
         
       
     
       FIG. 11  depicts an example method in accordance with some embodiments. The example method includes: providing a first connector having one or more retention springs, each retention spring having a retaining portion engageable with a retention feature of a second connector; providing a layer of compressive residual stress in the retention spring(s) by selective shot peening of a portion of each of the one or more retention springs proximal of the retaining portion, such as by a WPC treatment using a low or medium power; receiving the second connector within a cavity of the first connector, the retention spring(s) displacing laterally outward as the second connector is received; and engaging the retention feature with the retention spring to impart a retention force that secures the second connector to the first connector. 
     The above described embodiments are intended to illustrate examples of certain applications of the invention in relation to electrical connectors, and does not so limit the invention to these embodiments. It is appreciated that any of the components described in any of the embodiments may be combined and or modified in accordance with the invention. For example, an embodiment may include a combination of one or more of the backup springs described herein within an electrical connector or other such application, or may include one or more variations and equivalents to the features described herein as would be clear given the disclosure provided herein.

Metadata:
Filing Date: 20120907
Publication Date: 20141111
Grant Date: 20141111
Priority Date: 20120824
Inventors: WEBER DOUGLAS J.
MATSUYUKI NAOTO
Assignee: APPLE INC
CPC Classifications: [{"code": "H01R13/639", "inventive": true, "first": true, "tree": "[]"}, {"code": "H01R43/26", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01R13/6275", "inventive": true, "first": true, "tree": "[]"}, {"code": "H01R43/26", "inventive": true, "first": false, "tree": "[]"}, {"code": "Y10T29/49208", "inventive": false, "first": false, "tree": "[]"}, {"code": "H01R43/18", "inventive": false, "first": false, "tree": "[]"}, {"code": "Y10T29/49208", "inventive": false, "first": false, "tree": "[]"}, {"code": "H01R13/639", "inventive": true, "first": true, "tree": "[]"}, {"code": "H01R13/6275", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01R43/18", "inventive": false, "first": false, "tree": "[]"}]
Family ID: 50148374