INPUT/OUTPUT DATA CABLE

Abstract: Flexible input/output data cable for use with programmable controllers. The cable has a ground conductor, a logic level voltage conductor, and a number of signal tracks. The conductors are disposed on two or three layers of flexible plastics material in specified ways to give high immunity to interference and low inductive losses.

Description: - _ - This invention relates to an input/output (I/O) data cable for use in interconnecting the modular components of a programmable controller. A programmable controller comprises a processor which controls the operation of the system being controlled by receiving logic signals from a plurality of input modules and feeding logic signals to a plurality of output modules, the input and output modules being connected to the processor through respective data cables. Also the logic level voltage must be fed to the input modules, output modules and processor. The logic signals which pass between the processor and the input and output modules are subjected to considerable interference especially in the case when the system being controlled is a machine. Accordingly, it is necessary to ensure that the interconnecting data cables have high immunity f om such inter erence. It is known to interconnect the I/O modules and the processor by means of rigid bus-bars and data cables, the rigid structure allowing high immunity to be designed into the bus-bars and data cables. However, such rigid systems severely restrict the versatility of the . controller as regards its physical layout. Flexible ribbon conductors are known but these do not have the required immunity and also suffer from high inductive losses. It is an object of the present . invention to obviate ___ - - . - or mitigate the above disadvantages. According to one aspect of the present invention there is provided an input/output data cable for a programmable controller, the cable comprising a flexible laminate made up of three layers, each layer having a conducting part and an insulating part, the first of said layers being adapted to be connected to the system ground, the second of said layers being adapted to carry a logic voltage, and the third of said layers having a plurality of signal tracks for carrying data signals, wherein said first and second layers are adjacent. According to a second aspect of the present invention there is provided an input/output data cable for a programmable controller, the cable comprising a flexible laminate made up of two layers, each layer having a conducting part and an insulating part, the conducting part of the first of said layers having a single conductin track extending substantially across the whole width of the layer, and the conducting part of the second of said layer being formed by a conducting track extending over part of the width of said layer and by a plurality of signal tracks for carrying data signals. Embodiments of the present invention will now be described, by way of example, with reference to the accompanying drawings, in which: Fig. 1 is a top plan view of one embodiment of a data cable made in accordance with said one aspect of OMPI the present invention; Fig. 2 is a sectional view taken along the line II - II of Fig. 1-} Figs. 3ji, 3b and 3 are plan views of the three layers of the data cable of Fig. 1; Figs. 4a and 4b are perspective and elevational I ~ views respectively of a connector for use with the data I cable of Fig. 1; and Figs. 5a and 5b_ are plan views of the tλvo layers 10 of one embodiment of a data cable made in accordance with said second aspect of the present invention. Referring to Figs. 1 - 4 of the drawings, an input/ output data cable 1 for interconnecting the modular components of a programmable controller comprises a 15 flexible laminate assembly made up of three layers 10, 11 and 12 each having a conducting part and an insulating part. The layer 11 is used for the logic voltage; the _ layer 12 is used for the system ground and layer 10 is used for data signals. 20 As illustrated in Figs. 3a and 3_b the layers 11 and 12 each comprise a single copper track 110 and 120 attached to an insulating polyester strip 111 and 121 respectively. . At the ends of each of the copper tracks 110 and 120 there are provided contact tabs 114 and 124 respectively for 25 connection with a connector as hereinafter described. The layer 10 comprises a plurality of side-by-side signal carrying conductors 100 extending along the layer 10 and attached to an insulating polyester strip - - The data cable is formed by glueing the layers together one on top of the other to form a laminate structure so that the logic voltage carrying layer 11 and system ground layer 12 are adjacent and the data signal carrying layer 10 is on the exterior. An additional insulating strip 133 is laid on top of the layer 12. The resultant assembly comprises a flexible laminated cable having relatively wide area, tracks the adjacent layers being extremely close to each other. This arrangement provides high immunity and additionally minimises inductive losses along the data signal tracks due to the relative closeness of the logic voltage carrying layer 11. A suitable terminal 40 is illustrated in Fig. 4. and is adapted to be attached to each end of the data cable 1. The terminal 40 has a plurality of spaced contacts 41, end ones 41a and 41b contacting with the ' respective tabs 114 and 124 of the voltage level layer 11 and ground layer 12. Central contacts 41c engage respective tracks of the data signal layer 10. - The above described arrangement wherein the data signal layer 10 is adjacent the logic voltage carrying layer 11 is suitable for a system which has been designed to fail safe on occurence of a high logic voltage level. Thus, in the event of a short circuit between the data signal layer 10 and the adjacent layer, i.e. the layer 11, the system being controlled by the controller will OMPI IPO - - fail safe . Clearly if the system being controlled has been designed to fail safe on a logic level of zero then the data carrying layer 10 should be placed adjacent the grounded layer 12. These two alternatives are possible with the data cable of this invention since the data signal carrying layer is adjacent- only ore other layer. Referring now to Figs. 5a, and 5b a data cable is made up of two layers 21 and 22. The first of the layers 21 comprises a single copper track 210 attached to an insulating polyester strip 211, a contact tab 214 is provided for connection with a conductor of the type illustrated in Figs. 4a. and 4b. The second layer 22 comprises a copper track 220 extending across substantially half of the width of the layer 22 and a plurality of side-by-side signal carrying conductors 225. The track 220 and conductors 225 are attached to an insulating polyester strip 221 and the track 220 is provided with a contact tab 224. The data cable is formed by glueing the layers 21 and 22 together one on top of the other to form a laminate structure. In this embodiment of the data cable the logic voltage can be applied either to the track 214 or track 224 depending on the system design, ground being connected to the other track. OMPI . IPO

Claims: - fc - CLAIMS ' 1. An input/output data cable for a programmable controller, the cable comprising a flexible laminat made up of three layers, each layer having a conductive part and an insulating part, a first of said layers being adapted to be connected to system ground, a second of said layers being adapted to carr j a logic voltage, and a third of said layers having a plurality of signal tracks for carrying data signals, said first and second layers being adjacent. 2. An input/output data cable for a programmable controller, the cable comprising a flexible laminat made up of two layers, each layer having a conductiv part and an insulating part, the conductive part of a first of said layers extending across substantially the whole width of the layer, and the conductive part of the second of said layers being formed by a conductive track extending over part of the width of said layer and by a plurality of signal tracks for carrying data signals. 3. A cable according to claim 1 or claim 2, in • which each layer comprises a flexible plastics substrate and one or more metal strips secured there 4. A cable according to claim 3, in which the substrate is of polyester and the metal is copper. 5. A cable according to any preceding claim, in which the layers are secured together by glueing. 6. A cable according to any preceding claim, in which an additional insulating strip is secured to the top layer. 7. A cable according to any preceding claim, O including a terminal end portion of greater width than the remainder of the cable, the signal tracks occupying the centre of the terminal end portion and the other conductive parts being arranged at e i ther side of the signal tracks.

Inventors: CLARKE G
Applicants: CLARKE G, SQUARE D CO
Application year: 1979
Main classification: H01B7
IPC codes: H01B7, H01B11