Backplane for a modularly expandable programmable controller

A modular programmable controller comprising:

• a first backplane unit having first and third opposing surfaces and a second surface transverse to and between the first and third surfaces, said first backplane unit being adapted for mounting on a supporting structure with the first surface adjacent the supporting structure, said first backplane unit containing a data bus segment terminates at one end in a first connector portion accessible through the second surface and at the other end in a second connector portion accessible through the third surface;
• a central processing module adapted to be removably mounted on the third surface of said first backplane unit, said central processing module having a connector portion thereon which is adapted to mate with the second connector portion of said first backplane unit when said central processing module is mounted thereon;
• a plurality of second backplane units, each having first and third opposing surfaces and second and fourth opposing surfaces transverse to and between the first and third surfaces;
• a data bus segment in each of said plurality of second backplane units, the data bus segment in each second backplane unit comprising a printed circuit board mounted substantially parallel with the first surface on said second backplane unit, said circuit board having a plurality of electrical contacts on an edge thereof which extends through the second surface of said second backplane unit to form a first connector portion of the data bus segment, each data bus segment in a second backplane unit further comprising a first card edge connector mounted to be accessible through the fourth surface of said second backplane unit to form a second connector portion of the data bus segment, a flexible cable connecting the contacts on said printed circuit board to said first card edge connector, and a second card edge connector electrically connected to the contacts on said printed circuit board, said second card edge connector forming a third connecting portion of the data bus segment in said second backplane unit intermediate the second and fourth surfaces thereof and accessible from the third surface thereof, the first and second connector portions of the data bus segment being located so that when backplane units are assembled side by side the first connector portion of the data bus segment in one backplane unit mates with the second connector portion of the data bus segment in an adjacent backplane unit to form a continuous data bus through the assembled backplane;
• and
• a plurality of input/output modules adapted to be removably mounted on the third surfaces of said second backplane units, each input/output module having a connector portion thereon which is adapted to mate with the third connector portion of the data bus segment in the second backplane unit on which it is mounted.

An expansible backplane for a modular programmable controller including a central processing mlodule and a plurality of input/output modules adapted to communicate with the central processing module through a data bus, the input/output modules further being adapted to receive signals from and supply signals to external devices through field wiring, the backplane being formed of a plurality of interconnectable backplane units, one backplane unit for each controller module, each backplane unit for an input/output module comprising:

• a housing having first and second side walls and a seating surface transverse to the side walls against which an input/output module may be secured;
• first and second connector portions accessible from the seating surface adapted to mate with complementary connector portions of the associated input/output module when the module is secured against the seating surface;
• a data bus segment extending between the side walls, said data bus segment terminating in third and fourth complementary pluggable connector portions in the first and second side walls respectively, the third and fourth connector portions being located so that when backplane units are assembled side by side a connector portion in the first side wall of one backplane unit mates with the connector portion in the second side wall of an adjacent backplane unit to form a continuous data bus through the assembled backplane, the data bus segment further being electrically connected to the first connector portion;
• and
• field wiring connection means mounted in said housing intermediate the first and second side walls thereof and electrically connected to said second connector portion for the connection of external field wiring.