Patent Abstract:
Electrical resistance between a male part and a female part through a canted spring is disclosed using mathematical modeling. Increase or decrease in resistance can be quickly analyzed by looking at the equivalence resistance and the number of contacts at the input side, the output side, or both. The number of contacts may also be created by forming a dimple having a discontinuity.

Full Description:
CROSS-REFERENCE TO RELATED APPLICATION 
       [0001]    This is a regular utility application of provisional application No. 61/478,815, filed Apr. 25, 2011, and of provisional application Ser. No. 61/426,954, filed Dec. 23, 2010, the entire contents of each of which are expressly incorporated herein by reference. 
     
    
     BACKGROUND 
       [0002]    Aspects of the disclosed embodiments relate to electrical connectors. Canted coil springs may be used to electrically connect two parts. A first part is a female part such that a bore extends through the part and can receive a second part, which is a male part. The male part may be shaped similar to a pin, shaft, plug, shank or the like and may have an outer surface with a shape corresponding to the shape of the bore. The outer diameter of the pin is smaller than the inner diameter of the bore to allow insertion of the pin into the bore and removal of the pin from the bore. The inner surface of the bore includes a groove for retaining a canted coil spring, which may instead be located on the pin and the combination configured to be inserted into the bore. In conventional current conducting applications of canted coil springs, the pin is inserted into the bore such that the outer surface of the pin contacts the canted coil spring. The canted coil spring establishes a connection between the outer surface of the pin and the inner surface of the bore. Accordingly, the canted coil spring facilitates flow of electrical current between the two parts. 
       SUMMARY 
       [0003]    An electrical connector is provided. In one example, the connector comprises a piston, a housing, and a canted coil spring comprising a plurality of spring coils. Wherein a single groove is incorporated in the housing or in the piston but not both the housing and the piston. The single groove is configured for accommodating the canted coil spring. Wherein at least one of the spring coils has a dimple formed upon the coil to define a section having a discontinuity. 
         [0004]    According to aspects of the disclosure, an electrical connector for electrical applications uses a canted coil spring between two components to transfer current between them. In one embodiment, at least one of the components has a V-shaped groove to contact at least one coil of the canted coil spring at two contact points. In another embodiment, both components include a V-shaped groove to provide multiple points of contact per coil for increased current carrying capability and decreased contact resistance. In yet another embodiment, both components have a curved groove to provide continuous contact surfaces with at least one coil of the spring. In yet another embodiment, one or both of the grooves are configured to reduce both contact resistance between the two components and the canted coil spring, and path resistance during transfer of electrical current through the canted coil spring from one component to the other component. 
         [0005]    A method for increasing a number of contact points in a single groove electrical connector assembly is provided. The method comprising providing a housing; providing a piston; providing a canted coil spring having a plurality of spring coils; and providing a groove in the housing or in the piston but not both the housing and the piston. The groove being sized and configured for accommodating the canted coil spring. The method further comprising providing a dimple having a discontinuity formed upon at least one of the spring coils; and wherein the dimple forms two contact points when contacting the at least one of the spring coils with the dimple against a generally flat surface. 
         [0006]    In another aspect of the present assembly, an electrical connector is provided comprising a piston, a housing, and a canted coil spring comprising a plurality of spring coils. A groove is incorporated in the housing or in the piston or both. The groove is configured for accommodating the canted coil spring and a separate groove may be incorporated adjacent the groove for accommodating another canted coil spring. Wherein at least one spring coil of the plurality of coils has a dimple formed thereon to define a section having a discontinuity. 
         [0007]    In another example, all of the plurality of spring coils each comprising a dimple formed thereon to define a section having a discontinuity. 
         [0008]    In another example, the spring is formed from a multi-metallic wire. 
         [0009]    In another example, the housing has the groove and wherein the at least one of the spring coils has two contact points with the housing and two contact points with a generally planar surface on the piston. 
         [0010]    In another example, the piston has the groove and wherein the at least one of the spring coils has two contact points with the piston and two contact points with a generally planar surface on the housing. 
         [0011]    In still another example, an equivalent resistance for a circuit formed from the connector assembly is 50% less than an equivalent resistance formed from a circuit made from a similar connector assembly but without the dimple formed upon the coil. 
         [0012]    In a further aspect of the present method, a method of forming a spring is provided. The method comprising the steps of forming a plurality of coils from a wire, canting the plurality of coils in a same canting direction, and forming a dimple on at least one coil of the plurality of coils to form a section having a discontinuity. 
         [0013]    In yet another example, the method further comprises the step of forming a dimple on each of the plurality of coils. 
         [0014]    In yet another example, the method further comprises the step of welding two end coils to from a garter-type canted coil spring. 
         [0015]    In yet another example, the wire is made from a copper material. 
         [0016]    In yet another example, the wire is made from a multi-metallic w ire. 
         [0017]    In yet another example, the multi-metallic wire comprises a copper inner core and a high tensile strength outer layer. 
         [0018]    The method of forming the spring can further comprise the step of forming a second dimple on the at least one coil at a location opposite the dimple. 
         [0019]    A still further aspect of the present method is a method of increasing a number of contact points in a spring groove comprising the steps of providing a housing; providing a piston; providing a canted coil spring having a plurality of spring coils; and forming a common groove between the housing and the piston. The common groove can comprise two side walls and a groove bottom located therebetween. The method further comprising the step of providing a dimple having a discontinuity formed upon at least one of the spring coils and wherein the dimple forms two contact points against a generally flat surface of the common groove. 
         [0020]    In yet another example, the method further comprises the step of providing a dimple having a discontinuity formed upon all of the plurality of coils. 
         [0021]    In yet another example, the method further comprises the step of providing a second dimple having a discontinuity formed upon the at least one of the spring coils at a location opposite the dimple. 
         [0022]    In yet another example, the method further comprises the step of providing a second dimple having a discontinuity upon all of the plurality of coils. 
         [0023]    The method can include providing the groove bottom on the piston and forming a V-groove with the two side walls in a bore of the housing. 
         [0024]    The method can include providing the groove bottom in the housing and forming a V-groove with the two side walls on the piston. 
         [0025]    The various embodiments of the present electrical connector have several features, no single one of which is solely responsible for their desirable attributes. Without limiting the scope of the present embodiments as expressed by the claims that follow, their more prominent features now will be discussed briefly. After considering this discussion, and particularly after reading the section entitled “Detailed Description” one will understand how the features of the present embodiments provide various advantages. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0026]    The various embodiments of the present electrical connector will be discussed in detail with an emphasis on highlighting the advantageous features. These embodiments depict the novel and non-obvious electrical connector shown in the accompanying drawings, which are for illustrative purposes only. These drawings include the following figures, in which like numerals indicate like parts: 
           [0027]      FIG. 1  is a side cross-sectional view of an electrical connector according to one exemplary embodiment. 
           [0028]      FIG. 2  is a front cross-sectional view of the electrical connector of  FIG. 1 . 
           [0029]      FIG. 3  is a diagram of an electrical circuit representing contact resistances of the electrical connector of  FIG. 1 . 
           [0030]      FIG. 4  is a side cross-sectional view of an electrical connector according to another exemplary embodiment. 
           [0031]      FIG. 5  is a front cross-sectional view of the electrical connector of  FIG. 4 . 
           [0032]      FIG. 6  is a diagram of an electrical circuit representing contact resistances of the electrical connector of  FIG. 4 . 
           [0033]      FIG. 7  is a side cross-sectional view of an electrical connector according to another exemplary embodiment. 
           [0034]      FIG. 8  is a front cross-sectional view of the electrical connector of  FIG. 7 . 
           [0035]      FIG. 9  is a diagram of an electrical circuit representing contact resistances of the electrical connector of  FIG. 7 . 
           [0036]      FIG. 10  is a front cross-sectional view of an electrical connector according to another exemplary embodiment. 
           [0037]      FIG. 11  is an electrical circuit representing contact resistances and path resistances of the electrical connector of  FIG. 7 . 
           [0038]      FIG. 12  is a front cross-sectional view of an electrical connector according to another exemplary embodiment. 
           [0039]      FIG. 13  is a front cross-sectional view of an electrical connector according to another exemplary embodiment. 
           [0040]      FIG. 14  is a side partial cross-sectional view of an electrical connector according to yet another exemplary embodiment. 
           [0041]      FIG. 15  is a side partial cross-sectional view of yet an electrical connector according to exemplary embodiment. 
       
    
    
       [0042]    The following detailed description describes the present embodiments with reference to the drawings. In the drawings, reference numbers label elements of the present embodiments. These reference numbers are reproduced below in connection with the discussion of the corresponding drawing features. 
       DETAILED DESCRIPTION 
       [0043]    The detailed description set forth below in connection with the appended drawings is intended as a description of embodiments of an electrical connector with a canted coil spring and methods for using the same and are not intended to represent the only forms in which the present assemblies and methods may be constructed or used. The description sets forth the features and the steps for using and constructing an electrical connector with a canted coil spring and methods for using the same in connection with the illustrated embodiments. It is to be understood, however, that the same or equivalent functions and structures may be accomplished by different embodiments that are also intended to be encompassed within the spirit and scope of the assemblies and methods. As denoted elsewhere herein, like element numbers are intended to indicate like or similar elements or features. 
         [0044]      FIGS. 1 and 2  show an electrical connector  10  according to one exemplary embodiment. The electrical connector includes an input side  12  and an output side  14 . The input side  12  includes a generally flat contact surface  16 . The output side  14  includes a generally flat contact surface  22 . A canted coil spring  30  connects the input side  12  to the output side  14  and facilitates flow of electrical current from the input side  12  to the output side  14 . The canted coil spring  30  is formed by a plurality of coils  32  that are canted at an acute angle relative to a centerline           extending through the coils. The two end coils can be connected to form a garter-type spring. The canted coil springs discussed herein are similar to exemplary canted coil springs disclosed in U.S. Pat. Nos. 4,655,462; 4,826,144; 4,876,781; 4,907,788; 4,915,366; 4,961,253; 4,964,204; 5,139,243; 5,160,122; 5,503,375; 5,615,870; 5,709,371; 5,791,638; and 7,055,812 and in co-pending application Ser. No. 12/102,626, filed Apr. 14. 2008 and Ser. No. 12/767,421. filed Apr. 26, 2010. the contents of which are expressly incorporated herein by reference. Furthermore, the connectors discussed herein are similar to exemplary connectors disclosed in U.S. Pat. Nos. 4,678,210; 5,081,390; 5,411,348; 5,545,842; 6,749,358; 6,835.084; 7,070,455; and 7,195,523, the contents of which are expressly incorporated herein by reference. 
         [0045]    The coils  32  of the canted coil spring  30  contact the contact surface  16  of the input side  12  at a contact point  40 . The coils  32  of the canted coil spring  30  contact the contact surface  22  of the output side  14  at a contact point  44 . The point contact between the flat contact surfaces  16  and  22  and the circular or elliptical coils of the canted coil spring  30  is referred to herein as a purely mathematical concept. One of ordinary skill in the art w ill readily recognize that the actual contact between the canted coil spring  30  and the flat surfaces  16  and  22  occurs at small contact areas, respectively. The input side  12  transfers electrical current to the canted coil spring  30  through the contact point  40 . Accordingly, the transfer of current at the contact point  40  creates a first contact resistance RC 1 . The canted coil spring  30  then transfers the electrical current to the output side  14  through the contact point  44 . Accordingly, the transfer of current at the contact point  44  creates a second contact resistance RC 2 .  FIG. 3  shows an equivalent circuit representing contact resistances RC 1  and RC 2 . Contact resistances RC 1  and RC 2  are in series. Therefore, an approximate equivalent resistance. Req for the circuit of  FIG. 3  is computed using Ohm&#39;s Law and represented by equation 1 as follows: 
         [0000]      Req˜RC1+RC2   (1)
 
         [0046]    Assuming that the input side  12  and the output side  14  are constructed from the same materials and the contact points  40  and  44  are approximately the same size, then the resistances RC 1  and RC 2  may have substantially the same value, which is referred to herein as RC. Therefore, the equivalent resistance Req can be represented by equation 2 as follows: 
         [0000]      Req˜2 RC   (2)
 
         [0047]      FIGS. 4 and 5  show an electrical connector  100  according to a second exemplary embodiment. The electrical connector includes an input side  112  and an output side  114 . The input side  112  includes a first contact surface  116  and a second contact surface  118  that are oriented at an angle α relative to each other, which are more clearly shown in  FIG. 5 . Accordingly, the contact surfaces  116  and  118  form a V-shaped groove or V-groove  120 , the depth of which partially depends on the magnitude of the angle α. The output side  114  includes a flat contact surface  122 . A canted coil spring  130  connects the input side  112  to the output side  114  and facilitates flow of electrical current from the input side  112  to the output side  114 . The canted coil spring  130  is formed with a plurality of coils  132  that are canted at an acute angle relative to a centerline           extending through the coils. 
         [0048]    The V-shaped groove  120  of the input side  112  accommodates the canted coil spring  130  such that the canted coil spring  130  contacts the first contact surface  116  at a first contact point  140  and contacts the second contact surface  118  at a second contact point  142 . The canted coil spring  130  contacts the contact surface  122  of the output side  114  at a third contact point  144 . The input side  112  transfers electrical current to the canted coil spring  130  through the first contact point  140  and the second contact point  142 . Accordingly, the transfer of current at the first contact point  140  creates a first contact resistance RC 1 . Similarly, the transfer of current at the second contact point  142  creates a second contact resistance RC 2 . The canted coil spring  130  then transfers the electrical current to the output side  114  through the third contact point  144 . Accordingly, the transfer of current at the third contact point  144  creates a third contact resistance RC 3 . 
         [0049]      FIG. 6  shows an equivalent circuit representing contact resistances RC 1 , RC 2  and RC 3 . Contact resistances RC 1  and RC 2  are in parallel, and contact resistance RC 3  is in series with the equivalent resistance of RC 1  and RC 2 . An approximate equivalent resistance Req of the circuit shown in  FIG. 6  can be computed using Ohm&#39;s Law and represented by equation 3 as follows: 
         [0000]    
       
         
           
             
               
                 
                   
                     Req 
                     ~ 
                     
                       
                         RC 
                          
                         
                             
                         
                          
                         1 
                          
                         RC 
                          
                         
                             
                         
                          
                         2 
                       
                       
                         ( 
                         
                           
                             RC 
                              
                             
                                 
                             
                              
                             1 
                           
                           + 
                           
                             RC 
                              
                             
                                 
                             
                              
                             2 
                           
                         
                         ) 
                       
                     
                   
                   + 
                   
                     RC 
                      
                     
                         
                     
                      
                     3 
                   
                 
               
               
                 
                   ( 
                   3 
                   ) 
                 
               
             
           
         
       
     
         [0050]    Assuming that the input side  112  and the output side  114  are constructed from the same materials, and the contact points  140 ,  142  and  144  are approximately the same size, then the resistances RC 1 , RC 2  and RC 3  may have substantially the same value, which is referred to herein as RC. Therefore, Req can be represent by equation 4 as follows: 
         [0000]      Req˜1.5 RC   (4)
 
         [0051]    The equivalent resistance of the circuit in  FIG. 6  is about 25% less than the equivalent resistance of the circuit in  FIG. 3  by having the input side  112  contact the canted coil spring  130  at two contact points rather than only one. Accordingly, the electrical connector  100  is more efficient in conducting current than the electrical connector  10 . However, in certain applications the higher equivalent resistance provided by the connector  10  may be preferred. For example, an application may require a certain level of heat to be generated at the electrical connector. Accordingly, the connector  10  may be more suitable for such applications as compared to the connector  100 , because the higher equivalent resistance of the connector  10  causes more heat generation than the heat generation caused by the equivalent resistance of the connector  100 . 
         [0052]    If the input side  112  contacts the canted coil spring  130  at more than two contact points, then by designating n as the number of contact points between the input side  112  and the canted coil spring  130 , and assuming that all of the contact points have the same contact resistance RC, then the equivalent contact resistance Req of the connector  100  can be approximately represented by equation 5 as follows: 
         [0000]    
       
         
           
             
               
                 
                   
                     
                       Req 
                       ~ 
                       
                         
                           n 
                           + 
                           1 
                         
                         n 
                       
                     
                      
                     RC 
                   
                    
                   
                     
 
                   
                    
                   
                     
                       n 
                       = 
                       2 
                     
                     , 
                     3 
                     , 
                     4 
                     , 
                     … 
                   
                 
               
               
                 
                   ( 
                   5 
                   ) 
                 
               
             
           
         
       
     
         [0053]    Based on equation 5, when the input side  112  contacts the canted coil spring  130  at two contact points. Req˜1.5 RC, which is the scenario discussed above in the embodiment of  FIGS. 4 and 5 . As the number of contact points on the input side  112  increases, Req falls between 1 and 1.5. with Req˜1 for a very large number of contact points. Thus, one of ordinary skill in the art will recognize that the larger the number of contact points between the input side  112  and the canted coil spring  130 , the lower the equivalent contact resistance of the electrical connector  100  compared to similar structured connectors but with fewer contacts on the input side. 
         [0054]      FIGS. 7 and 8  show an electrical connector  200  according to a third exemplary embodiment. The electrical connector includes an input side  212  and an output side  214 . The input side  212  includes a first contact surface  216  and a second contact surface  218  that are oriented at an angle α relative to each other. Accordingly, the contact surfaces  216  and  218  form a V-shaped groove or V-groove  220 , the depth of which partially depends on the magnitude of the angle α. The output side  214  includes a first contact surface  222  and a second contact surface  224  that are oriented at an angle β relative to each other. Accordingly, the contact surfaces  222  and  224  form a V-shaped groove  226 , the depth of which partially depends on the magnitude of the angle β. A canted coil spring  230  connects the input side  212  to the output side  214  and facilitates flow of electrical current from the input side  212  to the output side  214 . The canted coil spring  230  is formed with a plurality of coils  232  (one coil shown in  FIG. 5 ) that are canted at an acute angle relative to a centerline           extending through the coils. 
         [0055]    The V-shaped groove  220  of the input side  212  accommodates the canted coil spring  230  such that the canted coil spring  230  contacts the first contact surface  216  at a first contact point  240  and contacts the second contact surface  218  at a second contact point  242 . The V-shaped groove  226  of the output side  214  accommodates the canted coil spring  230  such that the canted coil spring  230  contacts the first contact surface  222  at a third contact point  244  and contacts the second contact surface  224  at a fourth contact point  246 . The input side  212  transfers electrical current to the canted coil spring  230  through the first contact point  240  and the second contact point  242 . Accordingly, the transfer of current at the first contact point  240  creates a first contact resistance RC 1 . Similarly, the transfer of current at the second contact point  242  creates a second contact resistance RC 2 . Electrical current from canted coil spring  230  is transferred to the output side  214  through the third contact point  244  and the fourth contact point  246 . Accordingly, the transfer of current at the third contact point  244  creates a third contact resistance RC 3 . Similarly, the transfer of current at the fourth contact point  246  creates a fourth contact resistance RC 4 . 
         [0056]      FIG. 9  shows an equivalent circuit representing contact resistances RC 1 , RC 2 , RC 3  and RC 4 . An approximate equivalent resistance Req of the circuit shown in  FIG. 9  can be computed using Ohm&#39;s Law and represented by equation 6 as follows: 
         [0000]    
       
         
           
             
               
                 
                   Req 
                   ~ 
                   
                     
                       
                         ( 
                         
                           
                             RC 
                              
                             
                                 
                             
                              
                             1 
                           
                           + 
                           
                             RC 
                              
                             
                                 
                             
                              
                             3 
                           
                         
                         ) 
                       
                        
                       
                         ( 
                         
                           
                             RC 
                              
                             
                                 
                             
                              
                             2 
                           
                           + 
                           
                             RC 
                              
                             
                                 
                             
                              
                             4 
                           
                         
                         ) 
                       
                     
                     
                       ( 
                       
                         
                           RC 
                            
                           
                               
                           
                            
                           1 
                         
                         + 
                         
                           RC 
                            
                           
                               
                           
                            
                           2 
                         
                         + 
                         
                           RC 
                            
                           
                               
                           
                            
                           3 
                         
                         + 
                         
                           RC 
                            
                           
                               
                           
                            
                           4 
                         
                       
                       ) 
                     
                   
                 
               
               
                 
                   ( 
                   6 
                   ) 
                 
               
             
           
         
       
     
         [0057]    Assuming that the input side  212  and the output side  214  are constructed from the same materials, and the contact points  240 ,  242 ,  244  and  246  are approximately the same size, then the resistances RC 1 , RC 2 , RC 3  and RC 4  may have substantially the same value,which is referred to herein as RC. Therefore, Req can be represent by equation 7 as follows: 
         [0000]      Req˜RC   (7)
 
         [0058]    The equivalent resistance of the circuit in  FIG. 9  is approximately 33% less than the equivalent resistance of the circuit in  FIG. 6  by having the output side  214  contact the canted coil spring  230  at two contact points rather than only one. Furthermore, the equivalent resistance of the circuit in  FIG. 9  is about 50% less than the equivalent resistance of the circuit in  FIG. 3 , because each of the input side  212  and the output side  214  contacts the canted coil spring  230  at two contact points rather than only one. Accordingly, the electrical connector  200  is more efficient than the electrical connector  100  and the electrical connector  10  at transferring current from the input side to the output side. However, in certain applications the higher equivalent resistance provided by the connector  10  or the connector  100  may be preferred. For example, an application may require a certain level of heat to be generated at the electrical connector. Accordingly, the electrical connector  10  or the electrical connector  100  may be more suitable for such applications as compared to the connector  200 , because the higher equivalent resistances of the connector  10  or the connector  100  causes more heat generation than the heat generation caused by the equivalent resistance of the connector  200 . 
         [0059]    Based on the above, one of ordinary skill in the art will appreciate that the number of contacts between a canted coil spring, the input side and the output side can affect the equivalent resistance of the electrical connector. The greater the number of contacts between the canted coil spring, the input side and the output side, the lower the equivalent resistance of the electrical connector. In the embodiments of  FIGS. 7-9 , up to two contacts on the input side and two contacts on the output side are provided. For example, if up to four contacts on the input side and four contacts on the output side are provided, the equivalent contact resistance of the electrical connector is approximately 0.5 RC, assuming that contact resistances at all of the contacts are generally similar. 
         [0060]      FIG. 10  shows an electrical connector  300  according to one exemplary embodiment. The electrical connector includes an input or input side  312  and an output or output side  314 . The input side  312  includes a generally curved contact surface  316 . The output side  314  also includes a generally curved contact surface  322 . A canted coil spring  330  connects the input side  312  to the output side  314  and facilitates flow of electrical current from the input side  312  to the output side  314 . The canted coil spring  330  is formed by a plurality of coils  332  (one coil shown in  FIG. 10 ) that are canted at an acute angle relative to a centerline           (shown extending through the page in  FIG. 10 ) extending through the coils. 
         [0061]    The canted coil spring  330  may contact the entire contact surface  316  and the entire contact surface  322 , especially when the input side  312  and the output side  314  compress the canted coil spring  330 . In other words, the electrical connector  300  provides a lame number of contact points between the canted coil spring  330 , the input side  312  and the output side  314  as compared to the electrical connectors  10 ,  100  and  200 . Accordingly, the equivalent contact resistance of the electrical connector  300  is less than the equivalent contact resistances of the electrical connectors  10 ,  100  and  200 . 
         [0062]    In the embodiment of  FIG. 10 , the input side  312  and the output side  314  contact the canted coil spring  330  at a large number of contact points. Designating n as the number of contact points on each of the input side  312  and the output side  314 , and assuming that all contact points have the same contact resistance, the equivalent contact resistance of the connector  300  can be approximately represented by equation 8 as follows: 
         [0000]    
       
         
           
             
               
                 
                   
                     
                       Req 
                       ~ 
                       
                         2 
                         n 
                       
                     
                      
                     RC 
                   
                    
                   
                     
 
                   
                    
                   
                     
                       n 
                       = 
                       2 
                     
                     , 
                     3 
                     , 
                     4 
                     , 
                     … 
                   
                 
               
               
                 
                   ( 
                   8 
                   ) 
                 
               
             
           
         
       
     
         [0063]    Based on equation 8, when each of the input side  312  and the output side  314  contacts the canted coil spring  330  at two contact points. Req˜1, which is the scenario discussed above in the embodiment of  FIGS. 7 and 8 . As the number of contact points on each of the input side  312  and the output side  314  increases, Req falls between 0 and 1. with the Req approaching zero for a very large number of contact points (i.e., Req˜0 when n=∞ in a purely mathematical model of the electrical connector). Thus, one of ordinary skill in the art w ill recognize that the larger the number of contact points between the input side  312  and the canted coil spring  330  and the output side  314  and the canted coil spring  330 , the lower the equivalent contact resistance of the electrical connector  300 . 
         [0064]    The exemplary electrical connectors disclosed herein may he used in any application where electrical current is transferred from one part to another with a canted coil spring. For example, the input side can be a bore of an electrical outlet or socket and the output side can be the shaft of an electrical plug. Other non-limiting examples include a stem from a car battery and a clamp from a car engine, and an audio jack and an audio transmitter. Heat transfer properties of the electrical connectors discussed herein are analogous to their contact resistance properties. Accordingly, the same principles regarding efficient transfer of current depending on the extent of contact between the spring, the input side and the output side are equally applicable to heat transfer between these parts. For example, heat is transferred more efficiently from the input side to the output side through the spring  330  of the electrical connector  300  of  FIG. 10  than spring  230  of the electrical connector  200  of  FIGS. 7-9 . Similarly, heat is transferred more efficiently from the input side to the output side through the spring  230  of the electrical connector  200  of  FIGS. 7-9  than the spring  130  of the electrical connector  100  of  FIGS. 4-6 . Thus, the present disclosure is not limited to electrical connectors and is applicable to connections for heat transfer from one part to another. 
         [0065]    In the above embodiments only contact resistances are discussed, which are created because of the contact between the input side and the canted coil spring and between the output side and the canted coil spring. Referring for example to the embodiments of  FIGS. 7 and 8 , the coils  232  of the spring also create a path resistance as the current flows through the coils  232  from the input side  212  to the output side  214 . This path resistance is referred to herein as RP.  FIG. 11  is a circuit diagram that illustrates both the contact resistances RC and path resistances RP of the electrical connector  200  of  FIGS. 7 and 8 . Referring to  FIG. 8 , the section P 1  of the coil  232  between the contact point  240  and the contact point  244  creates a path resistance RP 1  as current flows from the contact point  240  to contact point  244 . Similarly, the section P 2  of the coil  232  between the contact point  242  and the contact point  246  creates a path resistance RP 2  as current flows from the contact point  242  to contact point  246 . Assuming that the coil sections P 1  and P 2  have the same geometry, have the same dimensions, and are constructed from the same materials, the values of RP 1  and RP 2  largely dependent on the length of the sections P 1  and P 2 , respectively. Accordingly, the closer the contact points are to each other, the lower the path resistance will be between the input side  212  and the output side  214 . The resistance created due to flow of electrical current through the canted coil spring from the input side to the output side is further described in co-pending patent application Ser. No. 12/691,564, filed Jan. 21, 2010, the contents of which are expressly incorporated herein by reference. 
         [0066]      FIG. 11  illustrates an equivalent circuit representing contact resistances RC 1 , RC 2 , RC 3  and RC 4 , and path resistances RP 1  and RP 2 . An approximate equivalent resistance Req of the circuit shown in  FIG. 11  can be computed using Ohm&#39;s Law and represented by equation 9 as follows: 
         [0000]    
       
         
           
             
               
                 
                   Req 
                   ~ 
                   
                     
                       
                         ( 
                         
                           
                             RC 
                              
                             
                                 
                             
                              
                             1 
                           
                           + 
                           
                             RP 
                              
                             
                                 
                             
                              
                             1 
                           
                           + 
                           
                             RC 
                              
                             
                                 
                             
                              
                             3 
                           
                         
                         ) 
                       
                        
                       
                         ( 
                         
                           
                             RC 
                              
                             
                                 
                             
                              
                             2 
                           
                           + 
                           
                             RP 
                              
                             
                                 
                             
                              
                             2 
                           
                           + 
                           
                             RC 
                              
                             
                                 
                             
                              
                             4 
                           
                         
                         ) 
                       
                     
                     
                       ( 
                       
                         
                           RC 
                            
                           
                               
                           
                            
                           1 
                         
                         + 
                         
                           RC 
                            
                           
                               
                           
                            
                           2 
                         
                         + 
                         
                           RC 
                            
                           
                               
                           
                            
                           3 
                         
                         + 
                         
                           RC 
                            
                           
                               
                           
                            
                           4 
                         
                         + 
                         
                           RP 
                            
                           
                               
                           
                            
                           1 
                         
                         + 
                         
                           RP 
                            
                           
                               
                           
                            
                           2 
                         
                       
                       ) 
                     
                   
                 
               
               
                 
                   ( 
                   9 
                   ) 
                 
               
             
           
         
       
     
         [0067]    Assuming that the input side  212  and the output side  214  are constructed from the same materials, and the contact points  240 ,  242 ,  244  and  246  are approximately the same size, then the resistances RC 1 , RC 2 , RC 3  and RC 4  may have substantially the same value, which is referred to herein as RC. Also, assuming that the sections P 1  and P 2  of the coil  232  have the same length, have the same geometry, have the same dimensions, and are constructed from the same materials, then RP 1  and RP 2  have substantially the same value, which is referred to herein as RP. Therefore, equation 9 can be rewritten as follows: 
         [0000]      Req˜RC+0.5 RP   (10)
 
         [0068]    The analysis provided above can be similarly applied to the other embodiments disclosed herein. Accordingly, the equivalent resistance for any electrical connector having two parts connected with a spring can be computed using Ohm&#39;s Law. Furthermore, an electrical connector can be designed to have a preferred equivalent resistance depending on the application in which the electrical connector is utilized. For example, for an application that requires an electrical connector with as low an equivalent resistance as possible, the number of contact points are increased (e.g. see the embodiment of  FIG. 10 ) and/or the distance between the contact points are reduced in order to reduce the path resistance. In contrast, for an application that requires an electrical connector with a high equivalent resistance, the number of contact points is reduced and/or the distance between the contact points are increased in order to increase the path resistance. 
         [0069]    As discussed below, increasing the number of contact points to reduce contact resistance does not necessarily lead to reduced path resistance or vice versa. Referring to  FIG. 12 , an electrical connector  400  is shown having a large number of contact points in a contact area CI because of substantially continuous contact between the input side  412  and the canted coil spring  430 . The output side  414  contacts the canted coil spring  430  at a contact point  444 . A section PI of a coil  432  extends from an edge  440  of the contact area CI to the contact point  444  with a radial length L 1 . A section P 2  extends between an edge  442  of the contact area CI to the contact point  444  with a radial length L 2 . Referring to  FIG. 13 , an electrical connector  500  is shown having two contact points  540  and  542  between the input side  512  and the canted coil spring  530 . The output side  514  contacts the canted coil spring  530  at a contact point  544 . The section P 1  of the coil  532  extends between contacts  540  and  544  with a radial length L 1 , and the section P 2  of the coil  532  extends between contacts  542  and  544  with a radial length L 2 . The equivalent contact resistance in the embodiment of  FIG. 12  is less than the equivalent contact resistance in the embodiment of  FIG. 13  because the input side  412  contacts the spring  430  with a larger number of contact points than the number of contact points between the input side  512  and the spring  530 . However, the equivalent path resistance in the embodiment of  FIG. 12  is greater than the equivalent path resistance in the embodiment of  FIG. 13  because the radial lengths L 1  and L 2  of the sections P 1  and P 2 , respectively, of the coil  432  are greater than the radial lengths L 1  and L 2  of the sections P 1  and P 2 , respectively, of the coil  532 . Thus, one of ordinary skill in the art will recognize from the exemplary embodiments of  FIGS. 12 and 13  that an electrical connector can be designed to provide a preferred contact and/or path resistance properties that are suitable for a particular application. 
         [0070]      FIG. 14  is a side partial cross-sectional view of an electrical connector assembly  600  according to yet another exemplary embodiment. The electrical assembly  600  may be referred to as a connector for a holding application incorporating a single groove  602 . As shown, the groove  602  is located on or in the housing  604  and not the piston or shaft  606 . The groove  602  on the housing  604  includes a first contact surface  616  and a second contact surface  618  that are oriented at an angle to one another to form a V-groove. However, other groove configurations having two slanted surfaces are contemplated. 
         [0071]    When in use as an electrical connector, electrical current transferring to or from the housing  604  to the canted coil spring  630  having a spring coil  632  as shown passes through two contact points  640 ,  642  located between the housing and the canted coil spring. Accordingly, the transfer of current at the first contact point  640  creates a first contact resistance RC 1  and transfer of current at the second contact point  642  creates a second contact resistance RC 2 . 
         [0072]    Although the current assembly  600  incorporates a single groove  602 , similar to the assembly  100  of  FIG. 5 , two additional contact points  644 .  646  are provided between the spring coil  632  and the surface  622  of the piston  606  to form a four contact point electrical connector. More specifically, the present assembly, device and method incorporate four contact points in a single groove holding application. For a single coil  232 , the four contact points are defined by two coil-to-housing contact points,  640 ,  642  and two coil-to-piston contact points  644 ,  646 . Accordingly, the transfer of current at the third contact point  644  creates a first contact resistance RC 3  and transfer of current at the fourth contact point  646  creates a fourth contact resistance RC 4 . 
         [0073]    Thus, although only a single groove is used in the present assembly and device, like the assembly of  FIG. 5 , the current assembly has the same equivalent resistance Req as the circuit shown in  FIG. 9  and is approximately 33% less than the equivalent resistance of the circuit in  FIG. 6 , which is the equivalent circuit for the assembly of  FIG. 5 . In one embodiment, the third contact point  644  and the fourth contact point  646  are formed by creating a dimple or arcuate surface  670  on the coil  632 . For example, the coil can be subjected to pressure or impact against an anvil, pressurized by a specially designed clamp, or other post coffin treatment processes. The dimple or arcuate surface  670  creates a section having a discontinuity formed upon the coil. The discontinuity alters the curvature of the coil to create multiple contact points between the coil and the piston. In the present embodiment, two contact points are created by the discontinuity. 
         [0074]    As understood, the present assembly, device, and method incorporate two contact points  644 ,  646  between a spring coil  632  and a surface  622 , such as a surface of a piston, and wherein the surface  672  is generally constant or flat between the two contact points. In an alternative embodiment, a complex groove may be incorporated on the piston, similar to a Mansard roof with a flat bottom and two tapered side surfaces, to provide four contact points between the spring coil and the piston, with two created by the dimple on the coil and two by the geometry of the Mansard roof. 
         [0075]    Thus, an aspect of the present method is further understood to include a method for forming a canted coil spring comprising coiling a wire to from a plurality of coils and canting the coils to cant along the same orientation. Forming a dimple on each of the plurality of coils to create coils with discontinuities for forming two contact points for each coil with a flat surface. The end coils can be welded to form a garter-type spring. In one example, the dimples can be created by pressuring or impacting the coils against one or more anvils. The anvils can have different sizes so that the dimples can be progressively formed to their final configuration. In another example, the coils can be pressurized by a specially designed clamp or other post coiling treatment processes. 
         [0076]      FIG. 15  is a side partial cross-sectional view of an electrical connector assembly  700  according to yet another exemplary embodiment. The electrical assembly  700  may be referred to as a connector for a holding application incorporating a single groove  702  and is similar to the assembly  600  of  FIG. 14 . However, in the present embodiment, the spring  730  having a spring coil  732  with a dimple or arcuate surface  770  is piston mounted. That is, the spring  730  is mounted in a groove  702  of a piston  706  as opposed to a housing  704 . The housing has a generally flat surface. Although only a single groove is provided, four contact points are incorporated in the present embodiment. Furthermore, the present spring  730  and the spring  630  of  FIG. 14  may be used in a two-groove configuration, with a groove in the housing and in or on the piston. Still furthermore, more than one spring may be used in parallel to decrease resistance. For example, two grooves  602  or  702  may be used side-by-side with two springs  630  or  730  in each of the grooves. In another embodiment, the groove  602  or  702  has a continuous contact surface with the coil  632  or  732 , similar to the embodiment of  FIG. 10  or  12 . Still furthermore, two dimples may be formed on each coil of the plurality of coils. The two dimples on each coil is preferably located at opposed positions or locations on each coil. 
         [0077]    In still yet another embodiment, a canted coil spring is provided having a plurality of coils. Wherein at least one of the coils of the plurality of coils incorporates a dimple defining a section of discontinuity formed upon the coil. In a prefer embodiment, a majority of the coils each having a dimple defining a section of discontinuity formed upon each coil. In yet another embodiment, all of the coils of the plurality of coils have a dimple defining a section having a discontinuity formed upon each coil. 
         [0078]    The material from which the canted coil springs discussed above is constructed affects both the contact resistance and path resistance for the above-discussed electrical connectors depending on the operating environment of the electrical connectors. For example, a highly electrically conductive material such as copper provides a lower contact resistance and a lower path resistance than steel. Thus, the use of copper for the canted coil spring would be preferred for efficient electrical conduction. However, in certain applications, a canted coil spring formed entirely from copper may not be suitable. Most materials with high electrical conductivity have a relatively low melting point, resulting in limited temperature resistance and therefore limited applications. Accordingly, canted coil springs made of these highly conductive materials may lose a significant portion of their mechanical properties at high temperatures, thereby causing the locking mechanism or the electrical contact to become less effective or fail altogether. The decrease in strength limits the force that can be applied to electrically conductive canted coil springs, thereby also limiting the use of these canted coil springs in certain applications, especially those applications that require high mechanical forces in environments with elevated temperatures. The canted coil springs of the above embodiments can be made in a multi-metallic configuration having a temperature resistant metallic core such as steel with a highly conductive outer layer such as copper. Alternatively, the core can be constructed from a highly conductive material such as copper, and the outer layer can be constructed from a temperature resistant material such as steel. The canted coil spring can also be constructed from more than two metallic or non-metallic layers in various configurations in order to provide preferred operational properties for an electrical connector in which the canted coil spring is used. For example, a third corrosion resistant layer may be incorporated to limit corrosion. Further details about constructing a canted coil spring from multiple materials can be found in U.S. Patent Publications 2008/0254670, 2010/0029145, and 2010/0289198, the disclosures of which are expressly incorporated herein by reference. 
         [0079]    One of ordinary skill in the art w ill readily recognize that the number of contact points may increase with the compression of the spring due to an increase in the contact area between the spring and the input side and/or the output side. The path resistance of the electrical connector may also decrease because of the compression of the spring. Thus, the operative compression range of the spring can be designed to provide preferred contact and/or path resistances for the electrical connector. 
         [0080]    Accordingly, as understood from the present disclosure, a connector may be provided with relatively low electrical resistance by increasing the number of contacts, decreasing the path of resistance, incorporating multi-metallic materials, or combinations thereof to produce a low system resistance compared to similarly structured connectors without similar use of contacts, lower path resistance, and/or multi-metallic materials. Another feature of the present disclosure is the use of closely-spaced coils to provide more contact points than comparable canted coil springs with greater coil spacing. 
         [0081]    The above description presents the best mode contemplated for the electrical connectors, in such full, clear, concise, and exact terms as to enable any person skilled in the art to which it pertains to make and use these connections. The electrical connectors, however, are susceptible to modifications and alternate constructions from that discussed above that are equivalent. Consequently, the electrical connectors are not limited to the particular embodiments disclosed. Furthermore, features, aspects, or functions specifically discussed for one embodiment but not another may similarly be incorporated in the latter provided the features, aspects and/or functions are compatible. For example, a connector may have both a continuous section contacting between a coil and a housing and as well as spaced apart contacts. Thus, the disclosure covers all modifications and alternate constructions coming within the spirit and scope of the disclosure as generally expressed by the following claims, which particularly point out and distinctly claim the subject matter of the disclosure.

Technology Classification (CPC): 8