Abstract:
The invention relates to a network wherein a distributor, particularly an Ethernet switch is used to increase the transfer speed and the volume of transmission active branching elements being connected thereto via the bus line.

Description:
TECHNICAL DOMAIN  
         [0001]    The invention relates to a network for connection by means of a programmable logic controller with at least one input/output unit via a bus line according to the features of the preamble of claim 1.  
         PRIOR ART  
         [0002]    For communication between programmable logic controllers (SPS) and input/output units in industry, for example within a machine, field bus systems (such as a profibus or an actuator/sensor interface bus) are conventionally used. These field busses can be implemented in two ways.  
           [0003]    First, each terminal device can have two connection points for a field bus connection, cabling thus taking place directly from device to device, and one of the devices being connected to a programmable logic controller. The second possibility is for the field bus to have a main line in which so-called branch points are located at the corresponding connection points for terminal devices, each respective terminal device being connected to its pertinent branch point.  
           [0004]    These field bus systems have proven themselves in practice. However, as a result of a maximum possible transmission rate of up to 10 megabits per second, the processing speed and data volume no longer is adequate for current applications. The low transmission rates are due to the fact that interfaces of terminal devices or branch points are built passively, so that an increase in the amount of data or the processing speed is not possible with these components.  
         DESCRIPTION OF THE INVENTION  
         [0005]    Therefore an object of this invention is to devise a corresponding network for connection of at least one programmable logic controller with at least one input/output unit that works reliably at high transmission rates in a rough and industrial environment.  
           [0006]    This object is achieved by the features of claim 1.  
           [0007]    It is provided as claimed for the invention that at least one programmable logic controller is connected to a distributor, especially to an Ethernet switch or any terminal device (for example, a Personal Computer (PC)), and via at least one active tap to at least one input/output unit that is connected to the distributor. As a result of the active tap, increased amounts of data can be transmitted and processed in a shorter time than would be possible with passive taps. Furthermore, the distributor is able to organize an entire data stream which flows between the respective input/output units and at least one programmable logic controller. To do this in an especially advantageous manner, at least one distributor either is made such that it sends data to a certain active tap or receives data from it or that it sends addressed data to the bus line and the respective active tap receives the data provided with its address. The same applies vice versa, i.e. at a respective tap to which at least one terminal device (input/output unit) is connected, data is addressed and sent to the pertinent programmable logic controller via the distributor.  
           [0008]    With one such network, as a result of the active construction of taps and distributor, such as an Ethernet switch, especially high transmission speeds (for example, up to 100 megabits per second) can be achieved. The active tap moreover has the advantage that in interplay with the distributor it can replace the existing field bus with its passive taps. Thus, in an especially advantageous manner the existing field bus networking can be replaced by Ethernet networking without new terminal devices or programmable logic controllers being necessary.  
           [0009]    An embodiment of the invention has the respective active tap with at least three terminals. Via a first terminal the tap is connected to the distributor or to another tap. A distributor or another tap can be connected likewise to a second terminal. Then the respective terminal device (input/output unit) is connected to a third terminal. Such a terminal device is not necessarily an input/output unit, but it is likewise possible that the connection is to only one sensor or only one actuator. Thus, star-like networking, or optionally several networks, is possible.  
           [0010]    For another embodiment of the invention, the terminals of the respective active tap are provided with quick connect technology. In addition to the known plug connections which are in use, quick connect technology is beneficial since quick connect technology is less complex and is easier to handle. While plug connections are designed to break the respective contact-closure, for example when the network is modified, and to re-establish it again, the quick connect technology is generally implemented only once, especially when the network is installed. Since only one-time contact closure is necessary, this can be easier (for example by insulation piercing contact-closure) so that material costs and installation costs can be kept low. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0011]    One sample network as claimed in the invention, to which the invention however is not limited, is shown in the Figure. 
     
    
     IMPLEMENTATIONS OF THE INVENTION  
       [0012]    Reference number  1  labels a network which is a so-called Ethernet network. At least one programmable logic controller  2  (SPS) (generally there being more than one such controller) and at least one input/output unit  3  (generally there being more than one such unit) are components of the network  1 . It now is provided as claimed for the invention that the programmable logic controller  2  on the one hand especially are directly connected to a distributor  4 . A bus line leads from the distributor  4 , and optionally also several bus lines  5  can be connected to the distributor  4 , via active taps  6 , to the respective input/output units  3 . A bus terminal can be connected to a last active tap  6  or can be integrated with this pertinent active tap  6 . The active taps  6  in the embodiment shown here each have terminals  7 , and the individual active taps  6  also can have a different number of terminals  7 . The first active tap  6  is connected with its first terminal via the bus line  5  to the distributor  4  which is a switch, a SPS or any terminal device (for example, PC), while a second terminal goes to another active tap  6 . The third terminal of the first active tap  6  is connected to another SPS  2  unit. For example, a sensor (or actuator)  8  is connected to the second active tap  6  and an input and output unit  3  is connected to the last active tap  6 . There also can be more or fewer than three active taps  6 . The terminals  7  are made in an especially advantageous manner by incorporating quick connect technology. Moreover, all of the components or some of the components of the network I can be designed according to protective technology (e.g., IP 65/67 protective technology). A supply of power for the active taps  6  can be provided via the bus line  5 , proceeding from the distributor  4  which can have an integrated power supply (power pack). Alternatively it also is conceivable to feed power into the bus line  5  via at least one feed point so the active taps  6  are supplied with voltage. This arrangement has the advantage that the bus line  5  is used for power supply and data transmission so that the installation and integration of a separate power supply line is eliminated. Separation of the bus line  5  and power supply also is conceivable. For example, at least one active tap  6  or several or all active taps  6  also can have their own power supplies.