GB2186442A - Transit for cables and pipes - Google Patents

Abstract

In a lead-through transit for cables 3 or pipes comprising a metal frame 1 having an opening 2 filled with lead-through blocks 4 and blanking blocks 5, each block 4 comprises complementary half-blocks 40 having an inner surface profiled to provide a plurality of closely spaced radially inward continuous projections 42 which are arranged to provide resilient deformation of the inner portion engaged by the cable 3 to accommodate in conformities in the cable. The projections 42 may be narrow annular ribs or be of saw-tooth or castellated sectional form (Fig 7). The transit includes a compression and packer system 7. <IMAGE>

Description

SPECIFICATION Improved transit for cables and pipes Description This invention relates to a transit providing a lead-through for electric cables or pipes that are required to extend through an opening in a wall, bulkhead, partition or the like. This invention concerns certain improvements in a particular kind oftransit as hereinafter defined and which is for use with cables, wires, pipes ortubes orthe like elongate elements commonly used in an installation for conducting electricity, service commodities such as gas, oil or water, or enclosing such service lines. For convenience herein, the term "cable" is used and should be interpreted in the context two include all such aforesaid elongate elements.

This invention is particularly concerned with a transit ofthe kind now defined as comprising a rectangular metal frame defining an opening through which the cables areto extend, a series of sets of modular blocks for assembly in rows within the frame opening, the blocks being adapted for surrounding each cable orfor blanking off a modular space, and a compression and packer assembly for mounting in the frame opening to clamp the assembled blocks together and around each cable with the compression and packer assembly completing filling ofthe frame opening.

Such defined kind oftransitforcables is well known and is disclosed in PatentSpecification GB 1,049,621.

Typically,transits ofthe defined kind are used in a wide range of applications and are installed in various environments including hazardous and have to meet specific regulations forfire-proofor flame-proof or gas-tig ht installations. Usually, a transit has to be assembled on site and often the working conditions at the installation site are difficult in many respects, such as:- access and location; the numbers, types and sizes of cable; limited working space and iack of access to both inlet and exit sides of the lead-through; and, ambient temperature, weather and environmental conditions.

Conventionally in transits of the defined kind, in each series set of the modular blocks, each block is of square section and has a length substantiallythe same as the depth of the metal frame into which the blocks are assembled in an array of superimposed rows. Each block in a set of blocks has the same external dimensions and a plurality of blocks from one set will completely fill one row across the inside of the frame.To provide blanks at locations in a row where no iead-through is required, each set includes solid blank blocks for assembly in the row. For a cable lead-through, the blocks have a through hole of a diameter corresponding to the diameter of the cable to be surrounded by the block, and to facilitate fitting and assembly each such block is formed in two complementary ha Ives with semi-cylindrical recesses that, when aligned, provide the lead-through hole in which the cable is seated.

The prior transit assemblies assume that cables have a smooth surface without irregularities and provide a plain internal surface for the lead-through passageway which engages with the cable.

Sometimes the size of the cableforwhich lead-through blocks are specified and provided is found on site to be outside the given nominal diameter and cannot be properly sealed to the half-blocks. Furthermore, cables are often not uniform in diameter along their length due to local deformation or manufacturing tolerances or defects or even because of special surface configurations.

In practice, the known cabletransistsofthe defined kind have a size lead-through blocks corresponding to each nominal cable size, and as a result extreme care is required to select the sized lead-through block equal to the diameter of the cable, and complications arise if the cables are not perfectly round and on-site measurements may be essential to obtain accurate fitting and sealing. Thus, for certain cables sized selection of lead-through blocks have to be made on site to ensure that certain cables can be accurately fitted in the transit.

In prior attempts to solve the problems arising with cables that do not fit a sized lead-through block, or if the actual sized block is not available, then it has been necessaryforthefitterto use packing strip material which is wound around the cable to increase it's diameterorto covera local defect.

Obviously, such extra stage required in the assembly by a fitter is both tedious and laborious as well as introducing a risk of inadequate sealing between the cable surface and the lead-through block. This is important bearing in mind the difficult conditions, possibly very dirty and the risk of contamination which arises by such intermediate stage of using a packing strip as well as the manual effort and time taken to apply such strip.

It is the object of this invention to provide a cable transit of improved construction which can be used either with cables which are not of uniform diameter, or which have surface irregularities, or which have a small variations in diameter along their axial length.

Other objectives and advantageous features ofthis invention will be referred to later herein.

According to this invention, we provide a transit of the defined kind for cables or the like characterised in that the lead-through block comprises two complementary similar halves for assembly together to define a lead-through passageway of substantially cylindrical form with the inner surface of the half-blocks that definethe passageway being profiled to provide a plurality of closely spaced radially inward continuous circumferential projections, and the material of the lead-through block being resiliently deformable so that on clamping and sealing the lead-through block to a cable extending through the passageway, the projections are resiliently deformed to accommodate inconformities in the cable surface and/or non-uniformity of cable diameterwithin limits determined by the deformation tolerance of the projections.

By this invention, it is possible to accommodate the common irregularities in the surface or the nominal diameter of the cable, in particularwhen nominal sized cables are found to be over-size or slightly oval.

Preferably, the radial inward projections are of annularform so asto present a pluralityofannular faces for sealing to the cable surface.

By this arrangement, each projection provides an annular sealing face for pressure engagementwith with cable surface and local deformation of one or more projections can accommodate irregularities or non-uniformity in the cable or the surface thereof.

It is preferred that the radial inward projections are evenly spaced apart along the axial length of the passageway. As a result ofthis even spacing ofthe projections, it is possible to determine the limits of deformation tolerance ofthe lead-through block for a passageway of a specified diameter. Thus, lead-through blocks can be provided with a specified tolerance limit for reference by a fitter during assembly and installation of a cable transit.

Conveniently, the radial inward projections can be formed as a series of annular ribs spaced evenly apart along the axial length ofthe passageway. The annular ribs may be oftapered form providing a narrow land for sealing engagement with the cable surface with the material of the rib being deformable to conform to any irregularity in the cable surface including diametric differences.

The annular ribs provide a continuous circumferential seal at each spaced axial location of the ribs sothata plurality ofannularseal faces are presented for sealing and clamping to the cable. By this arrangement, a discontinuity in sealing engagementwith the cable surface at one position will not prevent an adequate seal being maintained at other axially spaced positions. As will be understood, this special feature makes the lead-through blocks tolerant of common defects or irregularities in the cable surface such as burrs, snagged areas, cable casing defects, and in some instances when fitting to old cables, the surface deterioration by existing fittings leaving score marks or local indentations or projections.

The annular ribs may be of symmetrical form such as of regularwedge section with the innermost radial edge of each rib being a fine edge orfin. In other configurations, the annular ribs may be of saw-tooth section with the innermost radial edge of each rib being flat and the opposed side walls of each rib being offset or unsymmetrically inclined to each other Other features of this invention will now be described with reference to exemplary embodiments depicted in the accompanying drawings wherein Figure lisa front elevation of a cable transit according to this invention shown in the assembled position with cables in situ; Figure 2 is a partly sectioned side view of the cable transitshown in Figure 1;; Figure 3 is an isometric view of part of the compression and packer assembly; Figure 4 is a detail sectional view of part of assembly shown in Figure 3 and as indicated therein; Figure 5 is an isometrisview ofthe compression plate ofthe compression and packer assembly; Figure 6is a detail isometric view of a half-block of a lead-through block; and Figure 7is a detail isometric view of an alternative form of half-block of a lead-through block.

With reference to the drawings of Figures 1 and 2, the improved cable transit comprises a rectangular frame 1 defining an opening 2 through which cables 3 of different sizes extend. Each cable 3 is held within a lead-through block4whilst blank blocks 5fill the modular spaces of the opening where no cable is present. In known manner, the frame is for mounting orsupport in an aperture in a bulkhead or partition or the like (not shown) and the numbers and sizes of cables may vary from one installation to another. For simplicity of explanation ofthis invention, only a small number of cables are depicted and the assembly is not as complex as found in practice where tens of cables may have to be accommodated and installed at the site location.

In this embodiment, there is depicted three series of modular sized sets of blocks designated by the suffixes a, band c. Each series set has a common length corresponding substantiallyto the depth of the opening 2 and the frame 1. Each series set has blocks of substantially square section with the respective width and height dimensions of each set being selected to a common multiple so that a plurality of blocks of each setwill complete a rowor fill a modular space within the frame. Typical suitable modular dimensions are 90mm, 60mm and 30mm forthe square section blocks.

Each set of blocks is assembled in a row and to separate and support the assembled rows, stay plates 6 extend therebetween to locate on the marginal edges of the side walls of the frame 1.

In addition, the opening 2 is closed by a compression and packer assembly 7 which clamps and holds the rows of blocks in place and applies pressure to the blocks.

With reference also to Figures 3,4 and 5, the compression and packer assembly 7 comprises a pressure plate 8, three compression blocks, 9,10 and 11 each having a respective compressor stud 12,13 and 14 extending therethrough. Each compression block 9,10 and 11 has a respective rear support plate 15,16and 17 againstwhichthe rear head of each respective stud 12,13 and 14 engages. Each stud 12,13 and 14 extends through the respective block and through aligned openings in a front support plate 18 with respective nuts 19,20 and 21 being in threaded engagement with the free end ofthe associated stud projecting through the front support plate 18.

The pressure plate 8 is a rigid body having a planar underside 22 for engagement with the upper faces of the top row of blocks 5a, and an edge flange 23 on each side of the plate 8 provides location ledges overlying the upper marginal edges ofthe blocks as well as providing outer end lug portions that extend outwardly and engage the outer faces of the sides of the frame 1. The topside ofthe plate 8 has a flat central portion 24 and opposed inclined portions 25.

Each ofthe compression blocks 9,10 and 11 are made of a resilient material and the outer blocks 9 and 11 have respective through holes 26,27 that extend transverse and spaced from the respective axes of the compression studs 12 and 14. As best shown in Figure 4, a respective limit pin 28 is mounted in each through hole 26,27 and this pin 28 is arranged to engage the innerface ofthe top ofthe frame 1 and the inclined portion ofthe pressure plate 8 so as to limit the degree of deformation of the blocks 9 and 11 when compression loading is applied to the blocks in the direction of the axis ofthe limit pins as later explained.

The upperwall 29 oftheframe 1 is provided with a central clearance hole 30. A hexagonal shaped boss 31 is rigidly mounted on the upper wall 29 and projects therefrom aligned with the clearance hole 30. The boss has an internal blind threaded bore 32 and a compression bolt 33 is in threaded engagement within the bore 32 with the head 34 of the bolt 33 being accessible through the clearance hole 30 for rotation by a suitable tool. As should be appreciated, the bolt 34 can be unthreaded to extend into the void belowthe boss 31 when the central compression block 10 is notfitted, and the head 34 of the bolt will engage with the central portion 24 ofthe plate 8.

The compression blocks 9 and 11 are similar and have inner tape faces that lie adjacent to the opposed side faces of the central compression block 10. The central block 10 is generally in the form of a wedge with the opposed side faces diverging from the front of the block as well as converging towards each othertowards the underside of the block to present a flat underside face 35 engaging the flat central portion 24 of the plate 8. The inner taperfaces ofthe outer compression blocks 9 and 10 are complementary to the wedge faces of the central block 10. The underside faces of the compression blocks 9 and 10 are inclined and complementaryto the respective inclined portions 25 of the plate 8.

With reference also to Figure 6, each lead-through block4 is similar and comprises two complementary half-blocks 40 that are assembled together with the cable extending therebetween as shown in Figure 1 and as is generally known in cable transits of the kind defined.

All ofthemodularblocksareformedfroma resilient material which may be the same material as used for the compression blocks 9,10 and 11.

Each half-block 40 provides a substantially semicylindrical passageway 41 and the internal surface of the half-block is particularly profiled by a series of semi-annular ribs 42 that are closely spaced together along the axis ofthe half-block40.

Each rib 42 projects radially inwards into the passageway 41 and is of a section tapering to the free end to present a fine edge orfin 43forengagement with the surface of the cable. Each rib 42 has opposed side wal is so that a series of recesses or valleys 44 extend between each fin 43. Each rib 42 is independently deformable to accomodate local irregularities or other inconformities in the cable surface, and for such deformation, the relevant portions of the ribs may be displaced into the adjacent voids provided by the valley recesses 44.

In the assembled leadthrough block comprising the complementary pair of ha If-blocks 40, the ribs 42 extend continuously around the circumference of the passageway at the respective axially spaced positions of each rib, and by this arrangement, an adequate seal is provided around the periphery of the cable irrespective of local irregularities orthe like as discussed previously.

The radial length of each rib and the spacing of the ribs is selected to provide a degree oftolerance in the sizing ofthe lead-through, and a nominal cable diameter size would be specified for a particular lead-through block with a tolerant dimensions to be applied by a fitter when selecting a particular lead-through block for a cable.

Typically, the invention can be applied most usefully where a nominal size cable but is found to be oversize or out-of-round or has a localised series of surface blemishes or defects. By providing the deformable ribs 42, adequate deformation of the inner parts of the lead-through block can be achieved whilst ensuring adequate sealing to the cable surface.

With reference to an alternative form of half-block 140 as depicted in Figure 7,this half-block 140 has a series of semi-annular ribs 142 that are semi-annular defining the substantially semi-cylindrical passageway 141. In this form of half-block 140, the ribs 142 are of saw-tooth section with radially inwardly projections terminating in a flat land portion 143 for sealing engagement with the cable surface as aforedescribed. There are valleys or recesses 144 disposed between each projecting rib 142 and in the same manner as just described, the projecting ribs can be locally deformed to accommodate irregularities or inconformities in the cable surface.

Other forms and sectional shapes of the ribs can be used and are considered to be within the scope of this invention although it is preferred that the ribs taper radially inwards to provide the recesses adjacent each rib formation into which the resilient material of each rib may be displaced on local deformation.

It is envisaged that for an average lead-through block having an axial length of about 60mm, then at least four rib formations are required The rib formations may only extend in the central area ofthe lead-through blockwith the outer end portions of the passageway being plain semi-cylindrical surfaces to provide plane lands for sealing engagement with the cable surface at the inlet and exit zones of the cable through the lead-through block.

The cable transit as aforedescribed is assembled from the individual components, and firstlythe frame 1 is located in the structure with the runs of cables3 extending through the opening 2 of the frame 1. The fitter is presumed to have the selection of modular blocks 4for each cable and a number of blanking blocks 5.

As depicted in Figure 1,thelargestlead-through blocks 4c are used in the lower row, and firstlythe lower half-blocks 40c are set against the bottom innerwall of the frame 1 and each respective cable 3 is seated in the semi-cylindrical passageway and then the upper half-block40c is seated on top to form the lead-through block closing overthe cable and forming the lower row. The stay plate 6 is then inserted in place on top ofthe row of blocks with the marginal flanged edges of the stay plate 6 riding over the side edges of the frame 1 to locate the stay plate 6 in a similar manner asforthe pressure plate 8.

Preferably, the stay plate has a central web portion which is pierced or of mesh to prevent high rates of heattransferfrom one side to the other of the cable transitwhen installed.

The fitter then selects the next cables 3 to be located in the lead-through blocks 4b forthe next row and this row includes a blanking block 5. As for the first row, when the blocks 4b and block 5b are assembled another stay plate 6 is located overthe row of blocks.

Thethird row of blocks 4a and 5a isthen assembled in a similar manner, and all ofthe cable runs are enclosed by the selected lead-through blocks with the lower portion of the frame opening being filled by the rows of blocks and stay plates 6.

During this selective assembly by the fitter, if cables arefound to be irregularor out-of-round,then all that the fitter is required to do is to checkthatthe selected lead-through block is within the specified limit of tolerance for fitting to that cable, and no additional or special steps are required.

Once this selective assembly has been completed by the fitter, it is then necessary to apply pressure to the assembled blocks and cables to clamp and seal the blocks together as well as to seal such lead-through blocks to the cable. In addition, the remainder of the opening intheframe 1 must be closed or filled so asto present a completely sealed assembly through which the cables extend. This next stage to complete the assembly is by the component parts of the compression and packer assembly as previously mentioned.

The pressure plate8 is located overthethird row of blocks and seated over the assembled array of blocks and cables Due to the resilient nature of the blocks and the effect of the cables, pressure must be applied to the assembled blocks to compress the blocks around the cables to seal the lead-through blocks both around the cable and to clamp them together and againstthe side walls ofthe frame 1 and to the stay plates 6.

To apply this pressure, the compression bolt 33 is rotated to bring the head 34 into engagement with the flat central portion 24 ofthe plate 8 and on further rotation of the head 34 compressive forces are applied through the plate 8 to the assembled blocks.

Once the compressive forces are sufficientto leave a clearance space between the pressure plate 8 and the innerface of the top frame wall 29, the fitter can insertthe two outer compression blocks 9 and 11 in the clearance space clear ofthe compression bolt which only extends to the centre of the clearance space and does not interfere with the fitting ofthe two side blocks 9 and 11.

Following the insertion ofthetwo side compression blocks 9 and 11, the compression bolt 33 can be counter-rotated to return the bolt into the bore of the boss 31 leaving the central area overthe pressure plate 8 free for insertion of the central wedge shaped compression block 10 betweenthe two side blocks 9 and 11. The assembly ofthe rows of blocks and cables will continue to exert reactive forces on the pressure plate 8 tending to displace it towardsthetop wall of the frame, and thus tending to compress the blocks 9 and 11. To obviate the affect of these reactive forces, the limit pins 28 mounted in the compression blocks 9 and 11 restrict squeezing ofthe blocks.

Once the three compression blocks 9, 10 and 11 are received within the clearance, the front support plate 18 can be engaged overthefreeendsofeach ofthe compressor studs 12,13 and 14 of the respective nuts 19,20 and 21 placed in threaded engagement. The fitter then tightens each of the nuts 19,20 and 21 to apply compressive forces to the compression blocks so thatthethree blocks are brought into wedge clamping engagementwith each other and brought into engagement with the support plate 18.On tightening of the nuts, each of the compression blocks 9,10 and 11 is squeezed so as to cause resilient displacement of the block material in a direction transverse to the axis of each compressor stud thereby expanding the assembly both to fill the clearance opening between the pressure plate 8 and the frame 1 and to exert the required clamping pressure onto the assembly of blocks and cables beneath the pressure plate 8.

Accordingly, the compression and packer assembly7 completes the filling of the opening 2 in the frame 1 whilst also applying the necessary forces to the assembled rows of blocks and cables to ensure thatwhole assembly is sealedtogether and securely located against displacement.

The forces applied to the assembled rows ofthe lead-through and blank blocks are sufficientto cause the ribs of each lead-through block to be maintained in sealing engagement with the cable, and as previously described, each lead-through block is designed for use with more than one cable size and to be tolerant of local irregularities and non-uniform sections of cables.

As will be understood, the fitting ofthe cable transit arises in various environments, and the cable transit may be installed as described in the vertical position, but it may be installed horizontally where safe retention and ease of assembly of the blocks and other component parts is required. In addition, the fitter may have to work in elevated positions on ladders or in confined positions where the number of blocks with existing transits is excessive with one blockfor each size of cable. Thus, the cable transit of this invention provides many advantages over the prior art systems.

The exemplary embodiments described are simplifed for an understanding of this invention, and the numbers and relative dimensions ofthe blocks may be varied whilst maintaining the principles of modular sizes, and of course in known manner, more than one block may fill a modular space, for instance four small blocks as shown in rowe may fill a modular space in rowc.

The resilient material of which the lead-through and blanking blocks as well as the compression blocks are made can be of any suitable material which is flame-resistant, fire-resistant, water-resistant and resistant to effects of rodent attack, ageing, and temperature variations.

Throughoutthis Description, reference has been made to cables as this is the commonest form of use of transits through bulkheads, partitions or the like.

However, the invented cable transit can be used and applied to pipes or conduits and the term "cable" is not intended to be a limitation to the application and use of the invention noristheuseoftheterm "cable" to be interpreted as a limitation to the scope of thins invention.

Claims (10)

1. A lead-through transit for cables or pipes ofthe kind comprising a rectangularframe defining an opening through which the cables areto extend, a series of sets of modular blocks for assembly in rows within the frame opening, the blocks being adapted for surrounding each cable or for blanking off a modular space, and a compression and packer assembly for mou nting in the frame opening to clamp the assembled blocks together and around each cable with the compression and packer assembly completing filiing of the frame opening, and characterised in that the lead-through block comprises two complementary similar halves for assembly together to define a lead-through passageway of substantially cylindrical form with the inner surface of the half-blocks that define the passageway being profiled to provide a plurality of closely spaced radially inward continuous circumferential projections, and the material ofthe lead-through block being resiliently deformable so that on clamping and sealing the lead-through block to a cable extending through the passageway, the projections are resiliently deformed to accommodate inconformities in the cable surface and/or non-uniformity of cable diameterwithin limits determined by the deformable tolerance of the projections.

2. Atransitaccording to Claim 1 wherein said radial inward projections are of annular form so asto present a plurality of annularfacesforsealing to the cable surface.

3. AtransitaccordingtoClaim 1 orClaim2 wherein said radial inward projections are evenly spaced apart along the axial length of the passageway.

4. Atransit according to any one of the preceding Claims wherein said radial inward projections are formed as a series of annular ribs spaced evenly apart along the axial length ofthe passageway.

5. A transit according to Claim 4wherein said ribs are oftapered form providing a narrow land for sealing engagementwiththecablesurface.

6. Atransit according to Claim Swherein said ribs are of symmetrical form with the innermost edge of each rib being a fine edge orfin.

7. Atransitaccording to Claim 1 orClaim2 wherein said radial inward projections are of saw-tooth shape in section.

8. Atransitaccording to Claim 1 orClaim2 wherein said radial inward projections are of castellated shape in section.

9. Atransit according to any one ofthe preceding Claims and wherein the modular blocks are of square cross section.

10. Atransit substantially as hereinbefore described with reference to the embodiments as depicted in the accompanying drawings.