Abstract:
A proximity detector having a housing and issuing an output signal whose state is a function of the position of a target or of the frequency of passage of a target, where the detector parameters can be set by an operator using operator dialog facilities communicating with the detector by dialog signals. The dialog facilities are separated from the detector housing and can be incorporated into a connection block connected to the detector housing by a connecting cable which conveys the dialog signals and the detector output signal.

Description:
BACKGROUND OF THE INVENTION 
   The present invention relates to a proximity detector of the inductive, capacitive, magnetic or photoelectric type which has remote dialogue facilities in order to enable an operator to carry out, notably, a detector learning function. 
   Some proximity detectors have a learning mode in order that the range of the detector can be automatically adapted with respect to the surroundings and/or with respect to a target. In fact, the inherent detection range of such an apparatus can vary from one detector to another, and for the same detector can vary according to the environment and assembly conditions, especially for an inductive detector embedded in solid metal. Furthermore, certain applications need the ability to change detector sensitivity according to its use. It is therefore useful to be able to make range learning for a proximity detector take place where it is used. Such a detector is notably described in document EP1143620. 
   Other proximity detectors are used to monitor rotation. In the same apparatus, they combine the conventional functions of detecting the presence of a target with the functions of counting the information received by the sensor over a given time, in order to compare, for example, with a preset triggering frequency on the apparatus in such a way as to output a signal which is the result of this comparison. In this way, we obtain an apparatus which is suitable for dealing in particular with problems of under-or over-speed with respect to a nominal frequency. 
   Document EP1130403 describes a detector for monitoring rotation, in front of which passes a target for which we want to monitor the frequency of passage compared to a normal frequency of passage. This detector has operator dialogue facilities consisting of a pushbutton and a dialogue electro-luminescent diode (LED) on the detector. The pushbutton serves to set the detector into a working mode or a learning mode. The learning mode enables the detector micro controller to calibrate the normal frequency of passage and makes it possible to select a detector operating margin about this normal frequency. In the learning mode, the dialogue LED associated with the pushbutton serves, for example, to guide the operator in setting the required detector operating margin. 
   However, as the size of a proximity detector is often very small, it is difficult to incorporate directly into the product those operator dialogue facilities needed to perform the learning functions. Furthermore, proximity detectors are often placed in an environment which is hostile for human beings, notably when close to moving machinery. Thus any operator manipulation of a pushbutton which is directly mounted on the detector would then be potentially dangerous. 
   The purpose of the present invention is to overcome these disadvantages by proposing a solution which makes simple installation of the dialogue facilities possible while also guaranteeing operator safety. 
   SUMMARY OF THE INVENTION 
   In order to do this, the invention describes a proximity detector comprising a housing and issuing an output signal whose state is a function of the position of a target in front of the said housing or of the frequency of passage of a target in front of the said housing, the detector comprising dialogue facilities communicating with the detector by dialogue signals in order to permit an operator to set the parameters of the detector. According to the invention, the dialogue facilities are separate from the detector housing. 
   According to one characteristic, the dialogue facilities are incorporated in a connection block connected to the detector housing by a connecting cable which conveys the dialogue signals and the detector output signal. The connection block has an external connection connector for the detector output signal. 
   According to another characteristic, the dialogue facilities comprise a dialogue LED and pushbutton. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Other characteristics and advantages will become apparent in the detailed description which follows by referring to one method of production given by way of example and represented by the annexed diagrams in which: 
       FIG. 1  represents a functional diagram of a proximity detector according to the invention, 
       FIG. 2  shows one embodiment of a detector fitted with a connection block. 
   

   DESCRIPTION OF THE PREFERRED EMBODIMENT 
   With reference to  FIG. 1 , a detection apparatus has a housing  10 , for example of parallelepiped shape, fitted with a detection face  12 . This detection apparatus, called “detector” or “proximity detector” in the present document, is an inductive, capacitive, magnetic or photoelectric cell proximity detector. The detector is charged with detecting the presence of one or more targets  5  in front of the detection face  12  of housing  10 , in such a way as to issue an output signal  15 , generally a binary signal, which is either a direct function of the position of target  5  in front of detection face  12  for use as simple proximity detector, or a function of the frequency of passage of target  5  in front of detection face  12  for use as a rotation monitoring detector. On housing  10 , there is frequently placed a signaling LED  16  which, conventionally, is the image of output  15 . 
   As indicated previously, such a detector often includes a learning mode in order to enable an operator to adjust a certain number of parameters, such as, for example, the nominal frequency of passage of the target, the margin of operation or detector sensitivity, the selection of operating mode, etc. These parameters are determined by the operator who uses simple dialogue facilities  35  which are connected to the detector in order to do so. The dialogue facilities enable the operator to read certain information coming from the sensor and also to send information to the sensor. Adjustments may be carried out either during manufacture of the detector, or during its initial installation on site, or when a target  20  is positioned, and also, notably, during periodic maintenance. 
   In one preferred embodiment, dialogue facilities  35  of the detector include an input organ for sending informations to the detector, like a pushbutton  31 , and an output organ for reading informations from the detector, like a dialogue LED  32  (electro-luminescent diode), which communicate with the detector by dialogue signals  14 . Thanks to such dialogue facilities, it is then possible at low cost to institute simple adjustment procedures enabling an operator to set the detector parameters in a straightforward manner. It is also possible to envisage replacing pushbutton  31  by a rotary switch, for example. 
   Usually, these dialogue facilities  35  are positioned directly on the detector housing  10 . However, this simple solution sometimes presents problems, especially if the size of the housing  10  is not adapted for an easy installation of the dialogue facilities  35  (detector too small) or when the housing  10  is installed in a location which is dangerous for the operator (machinery surroundings). 
   For this reason, according to the invention, operator dialogue facilities  35  of the detector are located remote from detector housing  10 , in such a way that they are in an area that does not present any danger for an operator. 
   Advantageously, dialogue facilities  35  are then incorporated into a connection block  30  which is connected to housing  10  by connecting cable  20 . The electrical power supply of the dialogue facilities  35  comes from the detector. Thus, the invention describes distributed or remote dialogue facilities of a detector and not external dialogue facilities. One end of this connecting cable  20  is fixed to connection block  30 , for example by moulding. According to one preferred embodiment, the connecting cable  20  comprises a total of five conductors or wires in order to convey, on the one hand, dialogue signals  14  which are necessary for communication between dialogue facilities  35  and housing  10  and, on the other hand, the detector output signal  15 . 
   The output signal  15  from a detector is generally conveyed on two or three wires depending on the technology used for the connection (for example, AC/DC type connection in two-wire technology: “signal” and “−”, or DC type connection in three-wire technology: “+”, “−” and “signal”). For the dialogue facilities composed of pushbutton  31  and a dialogue LED  32 , the dialogue signals  14  are then conveyed on either three remaining wires in an AC/DC type connection, or on two remaining wires in a DC type connection. In this latter case, the two wires are used respectively for the signal from the pushbutton and for that from the LED, the common being connected to the “−” wire of the output signal  15 . 
   Connection block  30  also contains a connector for external connection  33  enabling output signal  15  from the detector to be made available on an external cable. This external connector  33  is, for example, of type M12, type K or other type. Equally, external connector  33  might also contain only those terminals onto which an external cable is to be connected in order to retrieve the detector output signal  15 . 
   Connecting cable  20  is sufficiently long so that connection block  30  is no longer situated in the danger zone of housing  10  but is nevertheless able to maintain connection block  30  and detector housing  10  close together. Typically, this length is of the order of five to fifty centimeters, and preferably from ten to twenty centimeters. 
   In a first variant, the other end of connecting cable  20  is directly fixed to detector housing  10 . This fixation is advantageously realized by moulding of connecting cable  20  on housing  10 . In this way, as shown in  FIG. 2 , each detector has systematically a connection block  30  which is fitted with dialogue facilities  35  for setting the detector parameters, and an external connector  33  for delivering output signal  15  from the detector. 
   In a second variant, detector housing  10  has a connector for internal connection  13 . This internal connector  13  makes it possible to connect and disconnect the other end of connecting cable  20  which is fitted with a connector that can mate with internal connector  13 . Advantageously, internal connector  13  and external connector  33  are of the same type so that an external connecting cable connected to one of the connectors  13 ,  33  can also connect to the other connector. In this way it becomes easy to insert a connection block  30  into an existing installation in order, temporarily, to benefit from dialogue facilities  35 . In fact, in an installation in which internal connector  13  of housing  10  of a detector is initially connected directly to an external cable, the operation consists of disconnecting the external cable from internal connector  13 , and then connecting a connection block  30  onto internal connector  13 , and finally to reconnect the external cable onto external connector  33  of connection block  30 . As the link cable  20  and external connector  33  of connection block  30  convey output signal  15 , the operation of the detector can then continue normally. This operation has the simple effect of inserting the dialogue facilities  35  of a connection block  30  between the detector and the external cable, in such a way as temporarily to carry out parameter setting functions on the detector. By performing the operation in reverse, it is easy to revert to the initial connection, removable connection block  30  then becoming available again, for example to set the parameters of other detectors. This variant therefore makes it possible to economise on the number of connection blocks used. It also makes it possible to ensure that no modification to detector parameter settings takes place inadvertently. 
   Thus, in the case where there is an internal connector  13  on housing  10 , this internal connector  13  is adapted in order that it can connect either with an external cable so that it delivers output signal  15 , or with a link cable  20  so that it delivers output signal  15  and dialogue signals  14 . Advantageously, a type M12 connector makes it possible to render all of these signals available on the same connector, use of any particular signal being then solely a function of the connections present on the mating connector present on the external cable and link cable  20 , that has just been connected to internal connector  13 . 
   It is clearly understood that, without departing from the scope of the invention, it is possible to conceive of other variants and detail improvements and even to consider the use of equivalent facilities.