Abstract:
A modular electric power distribution system distributes electric power between a power source and control modules for power consumers or other electronic components.

Description:
FIELD OF INVENTION 
       [0001]    The invention relates to a modular electric power distribution system for transmitting electric power between a power source and control modules for power consumers, which may be electric step motors. Power is transmitted in response to input signals received by circuitry in the control modules. A number of types of electric power may be transmitted between the power source and the modules. Each type of power is distributed to the modules depending upon the needs of power consumers controlled by the modules. Power may be transmitted from a power consumer back into the distribution system. 
       BACKGROUND OF THE INVENTION 
       [0002]    Electric power control modules supply power to step motors in response to input signals received by the modules. Each module may supply a number of different types of power. Conventionally, each module is connected to a power source by heavy-duty power cables. Two cables are required for each type of power supplied to a module. Each module includes a header connector which mates with a plug connector mounted on the ends of each pair of power cables supplying a type of electric power to the module. A number of power control modules are positioned together to facilitate connecting the modules to the power source and inspection and servicing of the modules. 
         [0003]    However, connecting each module to the power source using pairs of heavy-duty cables for each required type of electric power is difficult, expensive and inconvenient. Sets of different length power cables must be cut, terminated and connected to the modules and to the power source. The large number of cables must be properly routed between the power source and the control modules. This is a time-consuming and expensive process. Servicing the cables and modules can be difficult. 
         [0004]    Contact members on adjacent modules are connected by high voltage, high amperage bridge assemblies using one-piece copper conductors. These bridge assemblies have long conductor strips with copper U-bends at the strip ends. The U-bends hold the copper strips on the contact members. 
         [0005]    High amperage current flowed through conventional bridge assemblies can heat and weaken the copper U-bends sufficiently to reduce contact pressure between the conductor strips and the contact members. This can reduce current flow between modules. 
         [0006]    Accordingly, there is a need for an improved modular power distribution system which efficiently connects a power source to a number of control modules without having to connect a pair of cables from the source to each module for each type of power supplied to the module. The improved system should include pairs of modular power conductors extending between modules. The pairs of conductors for each type of power should be connected to the power source by power cables extending to a first or end module only and should be connected to additional modules by pairs of series-oriented conductors having modular distribution units and bridge assemblies connecting adjacent distribution units. The distribution units should be removably mounted on the control modules, and the bridge assemblies should be easily and removably mounted on the distribution units to facilitate installation and servicing. 
         [0007]    There is also a need for an improved bridge assembly with copper conductors and heat-resistant springs which hold the copper conductors against contact elements on the modules so that current heating of the conductors does not impair the springs and does not reduce current flow. 
       SUMMARY OF THE INVENTION 
       [0008]    One aspect of the invention is a modular electric power distribution system for connecting a power source to a number of control modules for electric devices. The electric devices may be electric step motors or other types of electric devices. 
         [0009]    Each control module requires one or more types of power supplied by the power source. The types of power include AC and DC power and power having different voltages and amperages. The modules may require up to 300 or higher amps at a voltage as high as 600 or more volts. A pair of power cables for each type of power extends from the power source to an end control module. Pairs of conductors for each type of power extend from the end module to the other modules. Each conductor includes a power distribution unit on each control module and bridge assemblies extending between adjacent distribution units. The power distribution units are connected to power contacts in the control modules. 
         [0010]    Each type of power is transmitted from the source through the two power cables and along the distribution units and the bridge assemblies to the control modules. Each module draws or returns power as required. Different length bridge assemblies connect control modules which are spaced apart different distances. 
         [0011]    The distribution system can connect electric components other than control modules for step motors. 
         [0012]    Another aspect of the invention relates to an improved bridge assembly for forming electrical connections between distribution units on adjacent control modules. The bridge assembly may be used to connect other types of electric power components. 
         [0013]    Each bridge assembly includes an insulating housing, two high-current bridge conductors and two spring clips in the housing. The conductors are made of highly conductive metal, which may be copper, with contacts at the ends of the conductors for forming electrical connections with distribution units or other components. The spring clips are made from heat-resistant metal, surround the contacts at the ends of the two bridge conductors and hold the conductors against plates in two distribution units to provide reliable, low insertion force mounting on the distribution units. The two conductors form two reliable electrical connections between the distribution units. The conductors and springs in each bridge assembly are mounted in the insulated housing to form a one-piece assembly and to prevent arcing to adjacent components and to prevent inadvertent contact by a technician. Resistance heating of the spring clips does not reduce contact pressure. 
         [0014]    A further aspect of the invention relates to an improved power distribution unit for mounting on a control module and forming electrical connections between a power source, circuitry in the module and bridge assemblies extending to other modules. The distribution unit includes upper level conductive plates with one or two upper bridge contact portions, a single lower level module contact, and an insulating body. Distribution units are removably mounted on control modules by extending the lower level module contacts into the control modules for electrical connection with circuitry in the modules. The ends of bridge assemblies engage upper level contact portions to form part of an elongate power conductor extending past a number of control modules. A pair of conductors with distribution units and bridge assemblies supplies one type of power to a number of control modules. 
         [0015]    The lower level module contacts in the distribution members may be closely spaced to engage closely spaced power contacts in control modules. The upper level bridge contact portions in the distribution members may be widely spaced to engage relatively wide bridge assemblies. The width of the bridge assemblies is determined by the spacing between bridge connectors in the assemblies, springs surrounding the contact ends of the bridge connectors, and an insulating housing surrounding the connectors and springs. 
         [0016]    The distribution members in the distribution units with closely spaced module contacts may include widely spaced upper plates and lateral steps between the module contacts and the plates. The plates engage the ends of the bridge assemblies from lower module contacts which engage power contacts in the modules. The upper and lower portions of the distribution members are fitted in an insulating housing. 
         [0017]    The upper level bridge contact portions may be spaced apart the same distance as the lower level contacts are spaced apart or may be spaced apart a greater or smaller distance than the lower level contacts, depending upon the requirements of a particular distribution system. When the spacing is different, distribution members may include lateral shift steps to provided offsets. The amount of offset in individual distribution members may increase across the distribution unit to space the upper portions evenly for engagement with evenly spaced bridge assemblies and to space the module contacts evenly for engagement with evenly spaced power contacts. 
     
    
     
       DESCRIPTION OF THE DRAWINGS 
         [0018]      FIG. 1  is a perspective view of a modular electric power distribution system according to the invention; 
           [0019]      FIG. 2  is a top view of  FIG. 1 ; 
           [0020]      FIG. 3  is a sectional view taken along line  3 - 3  of  FIG. 2 ; 
           [0021]      FIG. 4  is a sectional view taken along line  4 - 4  of  FIG. 2 ; 
           [0022]      FIG. 5  is a side view of a bridge assembly above a power distribution unit showing an alternative distribution unit; 
           [0023]      FIG. 6  is a sectional view taken along line  6 - 6  of  FIG. 5 ; 
           [0024]      FIG. 7  is a sectional view similar to  FIG. 6  showing the bridge assembly engaging the distribution unit; 
           [0025]      FIG. 8  is an exploded view of an end power distribution unit; 
           [0026]      FIG. 9  is a top view of power distribution members in the distribution unit of  FIG. 8 ; 
           [0027]      FIGS. 10 ,  11  and  12  are exploded views of power distribution units; 
           [0028]      FIG. 13  is an exploded view of a bridge assembly; 
           [0029]      FIG. 14  is a side view of a power conductor used in a bridge assembly; 
           [0030]      FIG. 15  is a bottom view of a cover taking the direction of line  15 - 15  of  FIG. 13 ; and, 
           [0031]      FIG. 16  is a sectional view taken along line  16 - 16  of  FIG. 13 . 
       
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0032]      FIG. 1  illustrates a modular electric power distribution system  10  according to the invention. The  FIG. 1  system forms two conductor electrical connections between an electric power source  12  and four or more control modules  14 . Each control module includes a rectangular body  16  with a top surface  18  and a mounting opening  20  formed in top surface  18 . The openings  20  are aligned in a row on surfaces  18 . Power contacts  22  are located in modules  14  below openings  20  for forming electrical connections with contacts in the lower portions of power distribution units  24  and  26  which extend into openings  20 . 
         [0033]    Each control module  14  is connected to an electric step motor or other power consumer. The module includes an actuator circuit which determines when power is required to be supplied to the step motor or consumer, or when power from the step motor or consumer is returned back to system  10 . The components of modules  14  and the actuator circuits are not illustrated. 
         [0034]    The power distribution system  10  includes pairs of elongate power conductors  28  extending across the tops of modules  14 . In  FIG. 1 , the system includes four conductors  28  to communicate two types of electric power between the source  12  and the modules. Two conductors  28  are required for each type of power distributed by system  10 . The system  10  uses as many pairs of conductors  28  as required to supply needed types of power to and receive power from the control modules. 
         [0035]    Power may be AC or DC and may be supplied at high amperage which may be as great as 100 amperes. The power may have a voltage as high as 600 volts. 
         [0036]    Each conductor  28  passes through an end power distribution unit  24  mounted on end module  14  and a number of like power distribution units  26  mounted on other modules  14 . Each conductor  28  also includes a number of bridge assemblies  36  which connect adjacent pairs of power distribution units  24  and  26 . End unit  24  on end module  14  is connected to power source  12  by heavy-duty, high amperage and high voltage power cables  34 . In  FIG. 1 , units  24  and  26  are shown partially inserted into modules  14 . 
         [0037]    The conductors  28  are connected to source  12 , extend through distribution units  24  and  26  on the modules and through bridge assemblies  36  between modules. Each distribution unit is connected to a power contact  22  in a module. Adjacent pairs of conductors  28  supply one type of power to the modules and can receive the same type of power back from the modules. 
         [0038]    Each power distribution unit  26  includes an insulated body with molded plastic upper contact housing  40  latched onto molded plastic lower contact housing  42 . See  FIG. 10 . Metal power distribution members  44  are fitted in recesses  46  in the upper plate housing  40  and in recesses  48  in the lower contact housing  42 . Each member  44  includes a flat, thick upper plate  50 , a central thick lower plate  52 , a lateral shift step  54  between the plates and a disconnect pin or module contact  56  on the bottom of the plate  52 . The plates are formed from copper to conduct high amperage current. In some units, steps  54  may not be used so that the upper and lower plates are aligned. 
         [0039]    Recesses  46  are spaced across the upper contact housing  40  for plates  50 , and recesses  48  are spaced across in housing  42  for plates  52 . Recesses  46  in upper plate housing  40  have a width sufficient to receive the relatively wide ends of the bridge assemblies  36  and form electrical connections with a pair of power conductors in each bridge assembly. A central opening  58  is provided in housing  42  at the bottom of each recess  48 . 
         [0040]    The top of each upper plate  50  includes upper contact portion  60  with contact surfaces  61  on both sides of portions  60 . The contact portions  60  are located on opposite plate ends for forming electrical connections with bridge assemblies  36  extending between adjacent distribution units. The distribution members  44  are formed from thick copper plate stock for reliable flow of high amperage and high voltage current through distribution system  10 . 
         [0041]    Power contact  56  on lower plate  52  is fitted in a recess in the bottom of lower housing  42  above opening  58 . The power contacts  56  are spaced closer together than upper plates  50  in the upper and lower housings. The different spacing is achieved by lateral shift or offset steps  54  between plates  50  and  52 . The contacts  56  are mounted on one side of lower plate  52 . The offset steps  54  and offset contacts  56  assure that upper plates  60  are uniformly spaced to fit in recesses  46  and  48  and that contacts  56  are uniformly spaced, closer together than plates  50 , and fit in the bottoms of recesses  48 . The upper portions of recesses  48  are spaced to receive the lower portions of upper plates  50  and are laterally offset from the bottoms of the recesses which receive the lower plates  52  and offset contacts  56 . 
         [0042]    Offsets or steps  54  on the two members  44  on one side of unit  32  locate contacts  56  closer to the center of the housing than upper plates  50 . The offsets  54  on the two members  44  on the other side of unit  26  also locate the contacts  56  closer to the center of the housing than plates  50 . Plates  50  are uniformly spaced, and the contacts  56  are uniformly spaced. This means that the offsets for the inner distribution members are smaller than the offsets for the outer distribution members  44 . The outer two distribution members  44  are identical but are rotated 180°, and the inner two distribution members  44  are identical but are rotated 180° to provide desired uniform spacing of the contacts  56  and uniform but wide spacing of plates  50 . 
         [0043]    Steps  54  shown in  FIG. 10  extend horizontally across members  44 . If desired, contacts  56  may be mounted on offset cut-out lower plates in members  44  which are connected to the upper plates by vertically extending lateral shift steps. 
         [0044]    The power contacts  56  illustrated in distribution unit  26  may be mounted on either side of the offset lower plates  52  of members  44  to provide lateral shift. 
         [0045]    Distribution units  26  have four power distribution members  44  with a horizontal lateral shift step in each member  44 . The steps space plates  50  from contacts  56 . Alternatively, a power distribution unit may have one flat center distribution member  44  without a lateral shift step. The plate  50  for the center member  44  would extend above a central contact  56 , without a lateral shift step. The plates  50  of the member  44  on one side of the center member would have an outer lateral shift step, as described. The plates  50  of the member on the other side of the center member would have an outer lateral shift step as described, and the members outside these members would have outer lateral shift steps greater than those of the adjacent members in order to maintain uniform spacing between plates  50  and uniform but closer spacing of the contacts  56  at the bottoms of the plates. 
         [0046]    If desired, a distribution unit may have a side power distribution member without a lateral shift step and progressively greater lateral shift steps in members to one side of the no-shift member. 
         [0047]      FIG. 8  is an exploded view of end power distribution unit  24 . Unit  24  includes an insulating body  64  with upper plate housing  66  and lower contact housing  68 . Four metal power distribution members  70  are positioned in the body. Members  70  are like previously described members  44  with the exception that each copper upper plate  72  includes opposed contact surfaces  74  at one plate end and a vertically extending power contact tab  76  at the opposite end of the plate. The upper and lower housings  66  and  68  are similar to previously described housings  40  and  42  with the exception that side cavities  78  are provided in housing  66  to receive tabs  76  and cable clamps  80  fitted on the tabs. The clamps are seated in cavities  78  with tabs  76  extending through central openings of the clamps. Cover  82  is latched onto housing  66  over the cable clamps  80  and includes spaced cable insertion openings  84  above the clamps. 
         [0048]    Stripped ends of power cables  34  are extended through the openings  84  in cover  82  and into the openings in the clamps. Electrical connections are formed between the power cables and the distribution members  70  by tightening clamp screws  86  which threadably engage the clamps. When each screw is tightened, a cable is clamped against a tab  76 , and an electrical connection is formed between the cable and a member  70 . 
         [0049]    In power distribution unit  24 , power contacts  88  on members  70  are located in recesses in the bottom of housings  68  and are spaced closer together than the plates  72  by lateral shift steps  90  in members  70 , as previously described. 
         [0050]    Tabs  76  and cable clamps  80  are wider than plates  72 . The tabs  76  on the outermost plates  72  are connected to the plates by 90° outward bends  92  and extend outwardly from the plates. See  FIG. 9 . The tabs  76  on the inner two plates  72  are connected to the plates by 90° inward offset bends  94  and extend outwardly from the plates. The inner tabs  76  are spaced a distance  96  out from the ends of the plates  72 , beyond the outer tabs  76 , to provide increased clearance between inner and outer tabs. Comparable clearance  98  is provided between the inner tabs at bends  94 . Clearances  100  are provided between inner tabs  76  and bends  92 . Positioning the tabs and wire clamps in spaced, wide cavities  78  with clearances separates members  70  and allows the plastic walls between the members to prevent arcing or creepage discharge between adjacent members when high amperage and high voltage current is distributed by system  10 . The plastic walls of insulating body  64  are not shown in  FIG. 9 . The bends  92  and  94  space the upwardly extending tabs  76  across unit  24  to fit in cavities  78 . 
         [0051]    Distribution members  70  are inserted into lower contact housing  68 , following which upper plate housing  66  is positioned on housing  68  with plates  72  in plate recesses  108  and  110  and tabs  76  extending into cavities  78 . The latch openings  106 , on the ends of housing  66 , snap around latch projections  112  to secure housings  66  and  68  together. The clamps  80  are fitted in cavities  78 , and cover  82  is latched onto upper plate housing  66 . 
         [0052]      FIGS. 11 and 12  are exploded views of power distribution units  172  and  174 , which are similar to unit  26 . Each unit includes a two-piece insulating body with upper and lower contact housings like body  38 . Each insulating body has interior recesses and surrounds two power distribution members. 
         [0053]    In  FIG. 11 , power distribution members  176  are like members  44  with the exception that the lower plate portions  178  are located inwardly of the upper plate portions  180  by inward lateral shift steps  182 . Module contacts  184  are mounted on the inner sides of lower plate portions  178 . 
         [0054]    In  FIG. 12 , the lower plate portions  186  are connected to upper plate portions  188  by outer, horizontal lateral steps  190 , and the module contacts  192  are mounted on the inner sides of the lower portions, as in distribution unit  26  illustrated in  FIG. 10 . 
         [0055]    In distribution units  24  and  26 , the module contacts  56  and  88  are socket contacts and engage pin-type power contacts  22  in the modules. As illustrated in  FIGS. 4 ,  6  and  7 , socket contacts on the lower plate portions may be replaced by pin-type contacts to engage socket contacts in the modules. 
         [0056]      FIG. 13  is an exploded view of a bridge assembly  36 . Bridge assembly  36  includes two flat copper conductors  114 , two stainless steel spring clips  116  which surround the ends of conductors  114 , and a plastic housing  118 , also shown in  FIG. 1 , which surrounds the conductors and clips. The housing  118  includes molded plastic housing base  120  and cover  122 . 
         [0057]    Each conductor  114  is formed from thick, conductive copper sheet stock and includes an elongate, flat conductor strip  124  extending along the length of assembly  36  with three contact arms  126  extending downwardly at 90° from each end of each conductive strip  124 . Slots  128  separate adjacent arms  126 . 
         [0058]    Clips  116  are formed from flexible, heat-resistant stainless steel. Each clip includes U-shaped upper portion  130  with three spaced individual spring arms  132  extending downwardly from the lower end of each side of portion  130 . The lower ends of arms  132  are bent inwardly to provide pressure ends  134  located inwardly from arms  132 . See  FIGS. 6 and 7 . When clips  116  are positioned on the ends of conductor strips  124 , ends  134  of spring arms  132  engage the lower ends of contact arms  126 . 
         [0059]    Plastic housing base  120  includes an elongate, circumferential wall or shell  136  which surrounds conductor strips  124  and top portions of clips  116 . Base  120  includes two three-sided arm shields  138  at each end of wall  136 . The open sides of shields  138  at each end of wall  136  face each other and partially surround contact arms  126  and spring arms  132  when the strips and clips are inserted into housing  118 . Contact projections  140  are provided on the inner surfaces of the lower ends of contact arms  126 . 
         [0060]    Contact clips  116  are fitted on the ends of the two conductors  114  with each clip arm  132  overlying a contact arm  126 , as illustrated in  FIGS. 6 and 7 . The spring arms  132  individually bias the contact arms  126  inwardly to form reliable individual electrical connections with the plates  50  and  72  in distribution units  24  and  26  when assemblies  36  are mounted on the units. Rectangular wall or shell  136  surrounds conductor strips  124 . The three-sided shields  138  at each end of the shell  136  partially surround arms  126  and  132  while allowing each arm  126  to contact plates  50  and  72  in the distribution units. The shields and arms  126  and  132  are separated by central slots  142 . Each slot receives a contact portion of a copper plate  50  or  72  when the bridge assembly is mounted on the distribution units. Three separate spring-backed and reliable electrical connections are formed between each conductor  114  and each plate  50 ,  72 . 
         [0061]    Housing base  120  includes a central bar  144 , shown in  FIGS. 6 and 7 , which is located inside shell  136  and extends between the ends of the shell midway between the sides of the shell. Bar  144  is between two recesses  146 , each located between the bar and one side of base  120 . Conductor strips  124  and the sides of upper clip spring portions  130  are positioned in recesses  146 . 
         [0062]    Cover  122  includes elongate top wall  148  which closes the top opening in base  120 . End lock tabs  150  extend downwardly from the ends of wall  148 . Two side lock tabs  152  extend downwardly from the sides of wall  148  between a pair of side walls  154  at each end of top wall  148 . A contact clip location projection  156  extends inwardly from each end of the top wall  148  between side walls  154 . Projections  156  and walls  154  define recesses for locating strips  124  and portions  130  of contact clips  116  in housing  118 . 
         [0063]    Conductors  114 , with clips  116  fitted around the ends of the conductors and spring arms  132  overlying contact arms  126 , are positioned in base  120  with the upper ends of the spring arms and contact arms in recesses  146  and bar  144  separating conductors  114 . Cover  122  is then latched onto base  120  with projections on end and side tabs  150 ,  152  latched into openings formed in shell  136 . Contact arms  126  extend parallel to the sides of assembly  36 , and conductor strips  124  fit between the clips  116  and bar  144 . Spring clips  116  are not stressed. The conductors  114  are loosely confined in housing  118 . 
         [0064]    Modular electrical power distribution system  10  is installed on a number of side-by-side power control modules by extending an end power distribution unit  24  in opening  20  in an end module  14  and fitting power distribution units  26  in the openings in the remaining modules. Power contacts  56  on the units  24  and  26  make electrical connections with module contacts  22 . Power cables  34  are secured to the power distribution members  70  in unit  24 , as previously described. 
         [0065]    Next, a pair of bridge assemblies  36  is mounted on adjacent distribution units  24 ,  26  for each type of power to be supplied to or received from modules  14 , as illustrated in  FIG. 1 . The assemblies  36  may have different lengths in order to connect distribution units mounted on different width modules. 
         [0066]    Bridge assemblies  36  connect adjacent units  24  and  26 . Each conductor  114  in the assembly forms an electrical connection between the copper plates in the units independent of the other conductor. The arm shields  138  at each end of bridge assembly  36  extend into recesses  46 ,  108  so that shields  138 , contact arms  126  and spring arms  132  are moved down and onto a plate. The thickness of the plate is greater than the rest spacing between contact projections  140 . During insertion, the beveled lead ends  160  of arms  126  engage plastic guiderails  162  which overly top edges  164  of the copper plates in units  24  and  26 . See  FIGS. 6 and 7 . Guiderails  162  extend between the end walls of the upper housings  40  and  66 . The rails  162  are beveled and spread arms  126  apart for movement of contact projections  140  onto the plates in the distribution units. The conductors  114  rotate in housing  118  during insertion into the distribution units. 
         [0067]    Spreading of arms  126  elastically flexes individual spring arms  132  outwardly to provide reliable, low-level contact pressure holding each projection  140  against the copper plates and forming three independent electrical connections between the plates and each end of each conductor  114 . The guiderails  162  provide touch safety when a bridge assembly  3  is not installed. 
         [0068]    During use of system  10 , high voltage and high amperage current flows along the bridge assemblies  36  between adjacent distribution units. The current flow may be sufficient to increase the temperature of the copper conductors  114 . The contact clips  116  are formed from a heat-resilient metal, which may be stainless steel, which does not lose its spring properties when heated by conductors  114 . This means that heating of the conductors does not decrease the contact pressure between conductors  114  and the plates in the distribution units and does not impair current flow. 
         [0069]    Conventional, high-current bridge assemblies use copper conductor strips which are joined together at the ends of the assemblies by integral copper U-bends. The U-bends hold the contacts at the ends of the assembly against inserted blades. High-current resistance heating of these conductors can heat and weaken the U-bends to undesirably reduce contact pressure with plates inserted between the ends of the conductors. 
         [0070]    Each end of each conductor  114  is electrically connected to each plate by three independent electrical connections at contact projections  140 . A separate spring arm  132  holds each contact arm against the plate at the connection so that possible degradation of one connection does not impair other connections. 
         [0071]    Each conductor  114  in a bridge assembly  36  conducts electricity between two plates. Typically, each conductor conducts one-half of the electricity conducted by the assembly.