Patent Publication Number: US-6222119-B1

Title: Cable connectors

Description:
This application claims priority under 35 U.S.C. §§119 and/or 365 to 9804154-4 filed in Sweden on Dec. 1, 1998; the entire content of which is hereby incorporated by reference. 
     1. Technical Field 
     The present invention relates to the technical field of cable connectors and in particular it relates to a device for environmentally protected connection of cables. 
     2. Related Art 
     Electronic equipment must often be protected from the ambient environment in order to function effectively. Negative effects on the function of the equipment include extreme temperatures, moisture, dirt, disruptive electromagnetic disturbance (EMC) and mechanical disturbance. The protection of the equipment usually consists of completely encapsuling the equipment. One problem with encapsuling is that the protection is often inadequate in the interface of the electronic equipment to the surroundings: power supply, signal cables etc. 
     An illustrative example of this problem is connectors for connecting incoming and outgoing cables to radio base stations placed outdoors. These radio base stations are climatized to keep a suitable operating climate for the equipment. The contacts are placed in the interface between two climate zones: the climatized zone inside the radio base station and the outdoor climate. If the surroundings are warmer than the climatized zone, the air will be cooled down at contact with the interface between the climate zones, and moisture in the air will condense, thereby subjecting the contacts to water and moisture, and this is particularly the case in areas having a warm moist climate. Moisture and water on the electrical contact surfaces can result in short-circuits or major disruptions in the flow of signals passing through the contacts. 
     WO95/28075 describes an EMC-shielding cable connector for circuit boards mounted in a magazine. According to this invention, the end of a cable coming from outside is provided with a box-shaped container which is pushed into a receiving container mounted in a hole in the wall of the magazine. The receiving container is then in electrical contact with both the cable protector and the wall of the magazine, and thus shields the circuit board against EMC. This known design, however, does not deal with the climate protection aspect. 
     A previously known solution to the problem of environmentally protecting connectors is to use special connectors designed for difficult environmental conditions. The disadvantage of this solution is that these connectors are very expensive. 
     Other known solutions to the same problem are to fix hoods of various designs and materials around the connector. This solution has a number of problems: 
     The protector is easily forgotten during installation and service. 
     Problems of visual inspection since the hood must be removed before beginning inspection. 
     Difficult to provide a comprehensive protection, and the connector can be subjected to moisture and dirt despite the protector. 
     Assembly and disassembly of the hood can be relatively time-consuming, making the installation and service costs unnecessarily high. 
     DESCRIPTION OF THE INVENTION 
     The present invention addresses the problem of how electrical equipment connectors can be securely, robustly and economically environmentally protected, i.e. protected against dust, EMC, moisture, extreme temperatures etc. 
     A purpose of the present invention is thus to achieve a device for cable connection in such a manner that the connector is securely protected against the effect of varying climate conditions. 
     Another purpose of the invention is to achieve a device for climatically protected cable connection in such a manner that the climatic protection can hardly be forgotten during installation and service. 
     An additional purpose of the invention is to achieve a device for cable connection in such a manner that it is relatively simple to make the connection itself, thus reducing installation and service costs. 
     In short, the invention involves placing the contacts inside a removable cassette provided with installation holes. This cassette can be placed in a space adapted thereto in a cabinet containing electronic equipment. The volume in the cassette is a special environmental zone separate from both the volume outside the protective shell of the cabinet and the rest of the volume inside the shell. At the interface to the outer environmental zone, the cables pass through an environmental seal while the contacts to the inner connections are at the interface to the inner climatic zone. In conjunction with the climate inside the shell, a good equalization between the environmental zones can be obtained for the equipment and the cassette. 
     Since the climatic protection is integrated with the cassette, which can be both opened and removed, installation and service will be simple since the cassette can be moved aside to a place where the work is relatively simple to perform. 
     Since the cassette is also made so that it is EMC-shielding, the electronic equipment will be in a volume which is both climatically and EMC-protected, at the same time as the contacts are climate-protected. 
    
    
     The invention will now be described with the aid of preferred embodiments and with reference to the accompanying drawings. 
     LIST OF FIGURES 
     FIG. 1 shows a cross-section of the device according to the invention mounted in a cabinet placed outdoors. 
     FIG. 2 shows a cross-section of the device according to the invention and how it divides up a volume into different EMC- and climatic zones. 
     FIG. 3 shows an embodiment of the device according to the invention, as seen in perspective. 
     FIG. 4 shows a cross-section as in FIG. 1 but with another embodiment of the device according to the invention. 
     FIG. 5 shows the embodiment according to FIG. 4 in essentially the same view as in FIG.  2 . 
    
    
     PREFERRED EMBODIMENT 
     FIG. 1 shows a cross-section through the device according to the invention mounted in a cabinet placed outdoors.  17  designates the cabinet containing electronic equipment  20 . The cabinet  17  comprises a door  21 , an internal wall  25  and a climate control unit  22  fixed to the inside of the door  21 . The climate control unit  22  controls in a known manner the climate in an inner volume “C”. The device itself according to the invention consists of a cassette I in which a number of cables  2  coming from outside and a number of internal cables  4  leading to the electrical equipment  20  are connected. The cables  2  enter the cassette  1  via a climatically protecting front  5  which, when the cassette  1  is provided with a number of ventilation holes (not shown), results in the cassette  1  being in essentially the same climate as the volume “C”. Since the cassette  1  is removable and since the cables  2 ,  4  are mounted with a certain amount of slack, the cassette  1  can be moved a certain distance without having to disconnect the cables  2 ,  4 . 
     FIG. 2 is cross-section which shows in more detail the device according to the invention mounted and how it divides up a volume into different EMC and climatic zones. In the figure,  17  designates, as in FIG. 1, a cabinet containing electronic equipment (not shown). The cassette  1 , cut away for the sake of illustration, is seen from the side inserted into the cabinet  17  through an opening  18  adapted thereto in the inner wall  25 . “A” designates a volume, either outdoors or indoors, which does  10  not necessarily have to be climatically protected or EMC-shielded. “C” designates a climatized volume in the cabinet  17 , in which the electronic equipment is housed. The volume “C” can be climatized by means of the climate control unit  22  shown in FIG. 1, if necessary.  15  designates an EMC-strip and  16  an environmental strip, placed either on the cabinet  17  or the front  5 , so that they completely surround the  15  opening  18  and still leave room for the attachment devices, e.g. screws  14   a,    14   b,  which attach the cassette  1  to the cabinet  17 . The environmental strip  16  is placed radially on the outside and thus protects the EMC-strip  15  as well. The EMC-strip  15  is along its entire length substantially in contact with both the cabinet  17  and the cassette  1 , both of which are substantially of EMC-shielding material, thereby obtaining EMC-shielding of the volume “C” as well. Since the environmental strip  16  is, along it entire length, substantially in contact with both the cassette  1  and the cabinet  17 , and since the cassette  1 , through a number of ventilation holes  10 , permits air to circulate to and from the zone “C”, a volume “B” is obtained in the cassette  1 , which is climatically protected. 
     FIG. 3 shows an embodiment of the device according to the invention as seen in perspective and with the same reference numerals as in FIG. 2. 1 designates a cassette essentially of metal or other EMC-shielding material. In one end of the cassette  1  there is a removable front  5 , comprising a front plate  7  and an environmental seal  6  of a known type. The environmental seal  6  is fixed to the front plate  7  in a known manner. The environmental seal  6  is provided with, and/or has the possibility of being provided with, a number of holes, one for each of the number of through cables  22  led through the front  5 . The entire front  5  is fixed to the internal wall  25  by means of screw-fasteners  14   a,    14   b  through screw holes  14  adapted thereto. 
     The upper surface of the cassette  1  in FIG. 3 is partially removed to show the passage of the cables  2  in the cassette to individual contacts  3 . The cables  2  go through the cassette  1  and each is provided at its extreme end with a contact  3 , the form of which depends on the purpose. They can, for example, be so-called D-subcontacts for signal transmission or contacts for power transmission. The contacts  3  are fixed in some manner, for example by means of screws  11 , in one of the walls of the cassette  1 , in this figure a rear plate  9 , which is provided with a number of contact holes (not shown), in order to make it possible for a number of chassis contacts  13  placed on the other side of the backplate  9 , to establish electrical contact with the contacts  3  in the cassette  1 . In the backplate  9  there are also those arrangements, e.g. screw holes (not shown), needed to fix the outer contacts  3  and the chassis contacts  13  to the backplate  9 . To the chassis contacts  13  there are connected a number of cables  4 , connected at their other ends to the electronic equipment (not shown), thereby coup-ling the incoming cables  2  to this equipment. The cables  2  and  4  are mounted with a certain amount of slack to make it possible to move the cassette a short distance without having to discontect the cables from the cassette. 
     In order for i.a. the chassis contacts  13  and the outer contacts  3  to be in essentially the same climate, a number of walls of the cassette  1 , in this case a cover  12  (partially cut away in the figure for the sake of illustration) and a bottom (not shown) are provided with a number of holes  10  arranged in such a manner as to preserve the EMC-shielding intact. Through these holes  10 , air can freely flow in a known manner and thus make the climate essentially the same for both the chassis contacts  13  and the outer contacts  3 . To facilitate installation and service, parts of the cassette  1 , in this case the cover  12  and the bottom, are removable since they are fixed, for example by means of screws, in such a manner that the EMC-shielding is intact. In order to be able to fix the cassette  1  securely in its intended location, it can be provided, for example, with a number of screw holes  14 , each having its counterpart at the location where it is to be mounted. 
     FIG. 4 shows the same view as FIG. 1, but with the essential difference that the device is mounted differently in the cabinet. In the figure, the cassette  1  is placed on and fixed to the bottom of the cabinet  17 . Otherwise, FIG. 4 is essentially analogous to FIG.  1 . 
     FIG. 5 shows in more detail the embodiment of the invention which is shown in FIG.  4 . The difference from the device in FIG. 2 is that the EMC-strip  15  and the environmental strip  16  in this figure are on the other side of both the cabinet  17  and the front  5 . In this case, the cassette  1  is not inserted into the cabinet  17  but is attached to the inside thereof. This makes it possible for the cassette  1  to be fixed to the floor of the cabinet  17 . 
     The form of the cassette  1  can vary to adapt it to the space for which it is intended. 
     The basic construction is the same, however, regardless of whether the cassette  1  is in the form of a rectangular prism, as above, as a cylinder, or in some other geometric shape. 
     When connecting cables, the installer performs, for example, the following steps (the service procedure does not differ substantially therefrom): 
     1. He unlocks and opens the door to the cabinet. 
     2. He unscrews the screws fixing the cassette to the cabinet. 
     3. He moves the cassette a short distance so that it is easy to work with. 
     4. He removes the front, cover and bottom. 
     5. He removes the environmental seal from the front plate. 
     6. If the cables from the electronic equipment are not already fixed to the container, he fixes these at their intended locations. 
     7. He threads the cables coming from the outside through the front plate. 
     8. He couples each of the cables coming from outside to the correct contact and fixes the contacts to the cassette. 
     9. If not already done, he prepares the environmental seal so that it has a number of holes corresponding to the cables coming from the front. 
     10. He mounts the environmental seal to the front plate seeing to it that the cables actually go through the holes intended for them in the front strip. 
     11. He mounts the front, cover and bottom. 
     12. He returns the cassette to its intended location and fixes it there. 
     13. He closes and locks the door. 
     Since the holes in the cassette  1  permit air to circulate through the interior (volume “B”) of the cassette  1 , to the protected inner volume “C”, this makes possible optimal climate equalisation between these volumes, which allows the climate to be essentially the same in these two volumes. This applies in whatever manner the inner volume “C” is climatized: with a heat exchanger, ventilation or the like, and when it is not climatized at all. Since the device according to the invention is designed to be EMC-shielding, the EMC-shielding of the inner volume is not affected appreciably. Thus, it should be apparent that the cable connections with the device according to the invention are climate protected at the same time as the EMC-shielding of the inner volume “C” is maintained. 
     Since the climate protection is integrated with the cassette  1  where the contacts  3  are placed, an assembler can hardly forget the climate protection during installation. This is especially true if the cabinet  17  is made so that it cannot be closed unless the cassette  1  is in its proper position. Furthermore, installation and service are relatively simple and rapid procedures since everything is easily accessible and no extra protectors need to be mounted or removed.