Background of the Invention Electronic circuits, particularly those which are located in positions where they may be exposed to the weather, are generally enclosed in a sealed casing. Cables which provide inputs and outputs to the circuits within the casing must enter the casing and a cable entry system provides apertures through which the cables enter. It additionally provides a seal around the cables where they enter the casing and prevents the electronic circuits within the casing being exposed to the external environment.

The type and number of cables which are required to enter the casing may change. The cable entry system needs to be able to facilitate changes in cable type, diameter and number.

Existing cable entry systems rely on the assumption that the number and size of the cables which are required to pass through it can be predetermined. Sealing around the cables is provided in this case by'O'rings, grommets or cable glands. However, such a system does not guarantee adequate sealing around the different types of cables that are liable to be used throughout the life of the enclosed circuits especially if the circuits are upgraded with further functionality and further or different cables are required.

Other custom designed cable entry systems rely on the number and size of cables being known before their design and use"O"rings to provide seals.

It would be desirable to provide a cable entry system which is adaptable to accommodate different forms and numbers of cables while providing adequate sealing around such cables.

Summary of the Invention According to one aspect of the invention there is provided a module, for a modular cable entry system comprising an arrangement of a plurality of modules wherein at least one of the modules provides for the passage of at least one cable, comprising a body defining an aperture sized to receive said one cable and having first and second configurations, wherein in the first configuration the module is arranged for receiving the cable in the aperture and in the second configuration portions of the body defining the aperture cooperate with the external surface of the received cable to form a seal therewith, said module being arranged when in the second configuration for releasable retention within the arrangement of the system.

In the first configuration, the body is arranged with the aperture for the cable sized so that it does not grip or hold the cable so that the cable is releasably retained such that it can be placed in and removed from the aperture.

According to another aspect of the invention there is provided a modular system comprising: an array of replaceable modules and releasable interconnection means, interconnecting and forming a weatherproof seal between said modules, wherein at least one of said modules has an aperture and retaining means which retains a cable in the aperture and forms a weatherproof seal between said at least one module and the cable.

The cable entry system of the present invention allows further additional or different cables to enter the casing. In particular it can accommodate cables of a presently unknown size and number, the size and number only becoming known at a future date when the functionality of the circuits within the casing is upgraded.

The cable entry system provides for the clamping of the cable or cables passing through it thus preventing damage within the casing when the cable is stressed or flexed.

For a better understanding of the present invention reference will now be made by way of example only to the accompanying drawings.

Brief Description of the Drawings Figure 1 illustrates a casing with a modular cable entry system and attached cables; Figure 2 illustrates a modular cable entry system without cables; Figures 3a and 3b illustrate an access module from the modular cable entry system in an assembled configuration with perspective views taken respectively from its front, top and left sides and its back, top and right sides; Figures 3c and 3d illustrate a blank module from the modular cable entry system with perspective views taken respectively from its front, top and left sides and its back, top and right sides; Figure 4 illustrates the component parts of an access module in a disassembled configuration with a perspective view taken from its top, front and left sides; and Figure 5 illustrates the component parts of an access module in a disassembled configuration with a perspective view taken from its top, front and right sides.

Description of the Preferred Embodiment Figure 1 illustrates a casing 2 for electronic equipment. The casing 2 houses a modular cable entry system 10 which allows electrical cables 18 to enter the casing 2 and provide inputs and outputs to the electronic equipment within the casing 2. The casing 2 is weatherproof and in combination with the cable entry system 10 prevents precipitation entering the casing 2. In particular, the modular cable entry system 10 makes a weatherproof seal with the casing 2 and with each of the cables 18. The cable entry system 10 is held in place within the casing 2 by a clamp 4, having a hinge 8 and lock 6. The hinge in this illustration is positioned so that the system 10 can be slid laterally into position in the casing. The hinge may also be positioned so that the system 10 can be placed into position by lowering it into the casing.

The cable entry system 10 be removed from casing 2 by releasing the lock 6, rotating the clamp 4 about the hinge 8 and sliding the system from the casing 2.

The cable entry system 10 is illustrated in more detail in Figure 2, which shows the system when it has been removed from the casing. Cables are not shown in this Figure for the purpose of clarity. The system is made up of a series of modular blocks namely access blocks 14, blank blocks 16 and end blocks 12. The access blocks 14 and blank blocks 16 form a 2 row by 5 column array of blocks. The array is five blocks in width, two blocks in height and one block in depth although the size of the array is only illustrative. Apertures 24 extend from the front face of the array through its depth to the back face of the array.

There are four end blocks 121,122, 123, 124. An end block 12 is attached to each of the extreme ends of the two rows in the array.

Each of the modular blocks 12,14,16 makes a weatherproof seal where it interfaces with an adjacent modular block.

Each of the access blocks 141,142, 143, 144, 145, 146, 147, and 148 has a substantially cuboid external casing. Each casings has one or more apertures 24 extending from the front face of the block, through the depth of the block to the back face of the block.

Each aperture is sized to allow a particular type of cable or cables 18 to pass through the access block and enter the casing 2. Each of the blank blocks 161 and 162 has a substantially cuboid external casing. The casing does not have any apertures. The end blocks prevent lateral movement of the access blocks and blank blocks when the system is inserted in the casing 2.

When the cable entry system 10 is removed from the casing 2 each of the modular blocks may be separated from the cable entry system. Any one of the access blocks 14 may be replaced by a access block 14 having a different number and/or sizing of apertures or a blank block 16. Any one of the blank blocks may be replaced by an access block. The cable entry system can therefore accommodate the addition or removal of cables 18 and the replacement of cables with one diameter by cables with a different diameter by simply replacing an existing access block or blank block.

Each of the access blocks 14 or blank blocks 16 which form a row of the array are joined laterally to the adjacent block in the array by a dovetail joint 32. Each end block is also attached to the end of a row of the array by a dovetail joint 32. Each dovetail joint 32 prevents relative movement of adjacent blocks in the row of the array in any direction other than the heightwise direction of the array. The dovetail joints 32 allow adjacent blocks to be interconnected in a releasable manner.

Each of the access blocks 14 and blank blocks 16 has on the surface of its upper face two parallel slots 34 and 36. Each front slot 34 is adjacent and parallel to the front face of the block and each back slot 36 is adjacent and parallel to the back face of the block. Each of the access blocks and blank blocks has protruding from the surface of its lower face two parallel ridges 38 and 40. Each front ridge 38 is adjacent and parallel to the front face of the block and each back ridge 40 is adjacent and parallel to the back face of the block. The slots 34,36 are sized to receive the ridges 38,40. Each row of interconnected access and blank blocks in the array consequently has on its upper surface front and back slots which run the length of the row and on its bottom surface front and back ridges 38 and 40 which run the length of the row. In the array, the front and back ridges 38 and 40 on the lower surface of upper row in the array are received by the front and back slots 34 and 36 projecting from upper surface of the lower row in the array.

Each pair of end blocks 12 at each of the extreme widthwise ends of the array are positioned one on top of the other and in combination form a wedge shape. The wedge has parallel planar faces flush with the upper, lower, front and back faces of the array. One plane of the wedge is flush with the side walls of the blocks at the end of the rows of the array. The sloped plane of the wedge makes an acute angle with this plane. The sloped plane has a pair of parallel slots 26 on its surface. The first slot 26 runs adjacent and parallel to the front face of the wedge and is continuous with the front slot 34 on,the upper face of the array. The second slot 26 is adjacent and parallel to the back face of the wedge and is continuous with the back slot 36 on the upper surface of the array.

The front and back slots 34 and 36 on the upper surface of the array and the front and back slots on the sloped plane of the end blocks are designed to engage with ridges at the perimeter of the receptacle in the casing for receiving the system. This allows the system to be slid into the receptacle. Likewise ridges 38 and 40 on the lower surface of the array are designed to engage with slots on the perimeter of the receptacle. Consequently the slots 26,34 and 36 and the ridges 38 and 40 hold the cable entry system 10 in place within the receptacle of the casing 2.

The access blocks 14 each comprise, in an unassembled or disassembled configuration, an upper block portion 20 and a lower block portion 22 as shown in Figures 4 and 5. These portions join together to form, in an assembled configuration, the access block 14 as shown in Figures 3a and 3b. For the purposes of clarity Figures 3a, 3b, 4 and 5 illustrate the external casing of the access block 14 and its component parts 20,22. Each of the component parts 20,22 of the casing is filled with thermoplastic or silicone gel shaped so that in the assembled access block the aperture or apertures 24 extend through the casing and the gel. The casing of the access block is formed by injecting moulding plastics.

Figure 3a illustrates an assembled casing of the access block 14. The view of the block is a perspective view showing the top and front faces and the left-lateral face 42 of the block. The block 14 has an upper portion 20 and a lower portion 22, parallel front and back slots 34,36 on its top surface and parallel front and back ridges 38,40 on its lower surface. Extending from the planar left-lateral face 42 is a projection 44. The projection 44 forms the tenon in the dovetail joint 32 made when the block is interconnected to another modular block as illustrated in Figure 2. The tenon 32 extends from the top face of the block to the bottom face of the block and is integral to and planar with those faces. The tenon has the shape of a truncated triangle when viewed in a cross-section taken parallel to the top face of the block, where the shorter of the parallel faces of the triangle is integral with the left-lateral face 42 of the block 14. The surfaces of the tenon which in cross-section form the other faces of the truncated triangle extend for the height of the block.

Figure 3b illustrates a different perspective view of the assembled casing of the access block 14. The view shows the top and back faces and the right-lateral face 52 of the block. The planar right-lateral face 52 of the access block 14 has a shaped slot 54 extending from the top surface of the access block 14 to the bottom face of the access block. The shaped slot 54 forms the mortice in the dovetail joint 32. The mortice 54 extends from the top face of the block to the bottom face of the block. The mortice 54 has the shape of a truncated triangle when viewed in a cross-section taken parallel to the top face of the block, where the shorter of the parallel faces of the truncated triangle is in line with the right-lateral face 52 of the block 14. The shaped slot 54 is shaped to receive a projection identical to the projection 44 illustrated on the left lateral face 42 in Figure 3a.

Referring to both Figures 3a and 3b, the interface between the upper and lower block portions 20 and 22 in the assembled configuration extends through the front face, a portion of the left-lateral face 42, the projection 44, a portion of the left- lateral face, back face, a portion of the right-lateral face 52, the shaped slot 54, and a portion of the right-lateral face of the access block 14. The aperture or apertures 24 in the access block 14 are positioned in alignment on the front and back faces of the block and overlap the interface between the upper block portion 20 and lower block portion 22 on those faces.

Figure 4 and 5 illustrate the casing of the access block 14 when in its unassembled or disassembled configuration. Figure 4 is a perspective view illustrating the front, left-lateral and top faces of the access block. Figure 5 is a perspective view illustrating the front, right-lateral and top faces of the access block 14. The figures make it clear how the upper block portion 20 and lower block portion 22 of the access block 14 are connected together in a releasable manner.

The portions of the left-lateral face 42 of the lower block portion 22 which interface with the left-lateral face 42 of the upper block portion 20 are vertically offset and recessed below the portions of the projection 44 of the lower block portion 22 which interface with the portions of the projection 44 of the upper block portion 20. The projection 44 on the upper block portion 20 extends from the upper surface of the block part way down the height of the upper block portion 20. A recessed portion 46 of the projection 48 extends the remaining distance down the height of the upper block portion 20. The surface of the recessed portion 46 is flush with the surface of the left-lateral face 42. The recessed portion 46 of the upper block portion 20 and the offset projection 44 of the lower block portion 22 are shaped and sized so that in the assembled configuration the offset portion of the projection 44 fits snugly with the recessed portion 46 to form the continuous planar faces of the tenon. The left-lateral face 42 of the upper and lower block portions interface to form a continuous planar face.

The vertically offset portion of the projection 44 of the lower block portion 22 has a slot 60 which extends parallel to the front and left-lateral faces of the block, heightwise for a length equal to the offset. A ridge 48 extends from the projection 44 of the upper block portion 20 parallel to the front and left-lateral faces to the edge of the upper block portion 20 through the recessed portion 46. The slot 60 and ridge 48 are sized so that the ridge fits snugly in the slot in the assembled configuration.

The portions of the right-lateral face 52 of the lower block portion 22 which interface with the right-lateral face 52 of the upper block portion 20 are vertically offset and raised above the portions of the lower block portion 22, defining the shaped slot 54, which interface with the portions of the upper block portion 20 which define the shaped slot 54. The portions of the upper block portion 20 defining the right-lateral face 52 of the block extend from the upper surface of the block part way down the height of the upper block portion 20. Recessed portions 56 of the right-lateral face 52 extend the remaining distance down the depth of the upper block portion 20. The surface of the recessed portion 56 is flush with the surface of the shaped slot 54 in the right-lateral face 52. The offset portions of the right-lateral face 52 of the lower block portion 22 form elongate members 64.

The recessed portions 56 of the right-lateral face 52 of the upper block portion 20 are sized so that in the assembled configuration the elongate members fit snugly with the recessed portions 56 so that the planar right-lateral face 52 extends continuously over the interface between the upper and lower block portions 20 and 21. In the assembled configuration the portions of the upper and lower block portions 20 and 22 which define the shaped slot 54 interface to form a continuous planar face.

Referring to Figures 4 and 5, a pair of releasable latches on each of the left and right sides of the casing of the access block 14 hold the two portions 20 and 22 of the block 14 in the assembled configuration. Each latch is formed by the engagement of a protrusion and a recess.

On the left-lateral side of the block casing, the latch protrusions 50 are wedge shaped and positioned on either side of the ridge 48 within the recessed portion 46 of the upper block portion 20 and the recesses 62 are also wedged shaped and positioned on a internal face of the offset protrusion 60 on either side of the slot 60. The offset protrusion is resiliently flexible and on joining the upper and lower portions of the blocks the offset portion flexes to allow it to move up and over the sloped faces of the wedge-shaped protrusions 50 and then snaps back to its equilibrium position to bring the wedge-shaped recesses 62 into engagement with the wedge-shaped protrusions 50.

This type of'snap-fit'latch is releasable.

On the right-lateral side of the block casing, each of the latch protrusions 58 are wedge shaped and positioned within the recessed portions 56 of the upper block portion 20. The portions of the lower block portion 22 which define the right-lateral face 52 and are offset from the portions that define the shaped slot 54 act as resiliently flexible members 64. The latch recesses 66 are also wedged shaped and each is positioned on an internal face of one of the resiliently flexible members 64. On joining the upper and lower portions of the blocks the resilient members flex to allow them to move up and over the sloped faces of the wedge-shaped protrusions 58 and then snap back to their equilibrium position to bring the wedge-shaped recesses 62 into engagement with the wedge-shaped protrusions 50. This type of 'snap-fit'latch is releasable.

Figures 3c and 3d illustrate a blank block 16 from different perspectives. Figure 3a illustrates the front, top and left- lateral faces of the block. Figure 3b illustrates the back, top and right-lateral faces of the block. The blank block 16 is the same as the access block 14 except it is formed from one part as opposed to two parts and does not have an aperture and like reference numerals indicate like features.

The assembly and disassembly of the system will now be explained. The access blocks are initially in their unassembled configuration as illustrated in Figures 4 and 5. Access blocks are chosen which have apertures 24 which are sized to receive the input and output cables for the electronic equipment in the casing 2. A first layer 70a and a second layer 70b of thermoplastic or silicone gel is placed into the interior of each of the upper and lower block portions 20 and 22 while the access block 14 is in the unassembled configuration as illustrated in Figure 4 by the arrows marked A. For each access block, the cable is placed in the part of the aperture defined by the lower block portion 22. The upper block portion 20 is aligned with the lower block portion 22 using the ridge 48 and slot 60. The portions are then moved together.

The offset portion of the protrusion 44 and the flexible members 64 move up and over their respective wedge-shaped latch protrusions 58 and 50 to latch the upper and lower block portions together in an assembled configuration and in addition urge the upper and lower portions into close cooperation. In this configuration the offset portion of the protrusion 44 fits snugly in the recessed portion 46 and the flexible members 64 fit snugly in the recessed portions 56. Thus a weatherproof seal is formed at the interface between the upper and lower block portions. The surface of the cable is gripped by portions of the casing of the access block 14 defining the aperture and by the gel inside the casing. These prevent movement of the cable relative to the access block 14 and ensure a weather-proof seal between the cable and the access block 14. A series of such access block is created dependent upon requirement. These access blocks are interconnected by using their tenons 44 and mortices 54 to form dovetail joints with adjacent blocks. Linear arrays of blocks can thus be formed. When an access block is interconnected to adjacent blocks, the block becomes locked into its assembled configuration and cannot be disassembled into its component parts until it is disconnected from the adjacent blocks.

The linear arrays can then be joined using the front and back grooves 34,36 on the top surface and the front and back ridges 38,40 on the bottom surface to form a two dimensional array. The system is then completed by adding end blocks using dovetail joints at the extreme ends of the array. The engagement of the tenons 44 and mortices 54 in the dove tail joints 32 and the ridges 40,42 and grooves 34,36 provide for a weather-proof seals between the modular blocks.

The assembled system 10 is then slid into a receptacle in the casing 2. The perimeter of the receptacle has ridges-for engaging the grooves 34,36 and 26 of the system 10 and grooves for engaging ridges 38,40 of the system 10. These engagements provide for a weather-proof seal between the casing 2 and the system 10, and also prevent movement of the system within the casing.

As all the connections between the system 10 and the casing 2, the modules 12,14,16 and the upper and lower block portions of the access blocks 14 are releasable, the disassembly of the system 10 is simply the reverse procedure to the disassembly of the system 10 is simply the reverse procedure to assembling the system 10.

The modular blocks are typically made by injection moulding plastics.