US2636922A - Strip-grip for electric cables - Google Patents

Description

April 28, 1953A v R. w. ATKINSON 2,636,922

STRIP-GRIP FOR' ELECTRIC CABLES Filed 001:: 23. 1948 2 SHEETS-SHEET l ATTORNEYS April 28, 1953 R. w. ATKINSON STRIP-GRIP FOR ELECTRIC CABLES Filed Oct. 23. 1948 2 SHEETSf-SHEET 2 ATTORNEY S Patented pr. 28, Y1953 2,636,922 y STRP-GRIP FOR ELECTRIC CABLES Ralph W. Atkinson, Westiield, N. J.,I assigner to General Cable Corporation, New York, N. Y., a corporation of New Jersey Application October 23, 1948, Serial No. 56,227

15 Claims.

This invention relates to high tension electric cables of the type in which insulated conductors are loosely enclosed by a pipe which is filled with an insulating iiuid under pressure. Usually the pipe is a rigid pipe into which one or several insulated conductors have been drawn, and the insulating fluid usually is an oil or an inert gas such as nitrogen. Such cables are the subject of the Sonnenfeld Patent 2,250,239.

More particularly, the invention relates to means for anchoring the insulated conductors against movement in the pipe at desired locations, such movement resulting from expansion and contraction of the conductors caused by variations in temperature during operation of the cable. This problem is of prime importance at semi-stops in the pipe, in which each insulated conductor, usually at a point near its connection to another insulated conductor, passes through an opening in a barrier plate across the pipe and is engaged by a packing gland or the like. The packing gland closes the opening around the insulated c-onductor and compresses the conductor insulation around its entire circumference. The purpose of this arrangement is to restrict movement of the insulating fluid longitudinally along the pipe substantially to the amount which migrates through the compressed conductor installation Where the conductors pass through the barrier plate.

lt is an object of the invention to provide improved means for securing an insulated conductor against longitudinal movement at desired locations in the pipe under all operating conditions, and for doing this without damage to the conductor insulation. lt is an object of the invention to provide improved means for anchoring the cable conductors at a semi-stop without the necessity of applying pressure on the insulation under the packing gland sufficient to hold the conductor against movement or to damage the insulation. it is a further object of the invention to provide improved joints for cables of the type described. Other objects and advantages of the invention will appear hereinafter.

A preferred embodiment of the invention has been selected for purposes of illustration and description and is shown in the accompanying drawings, wherein:

Figure l shows end portions of two lengths of Pipe type cable and a semi-stop joint therefor7 part of the joint casing being broken away to disclose the construction;

Figure 2 is a view to enlarged scale of the lefthand portion of Figure l, showing details of the semi-stop construction more clearly;

Figure 3 is a view to enlarged scale of the lefthand portion of Figure 1, showing details of the means for anchoring the conductors against movement;

Figure 4 is a transverse section to enlarged scale through the cable joint substantially on the line 4-6 of Figure 1; and

Figure 5 is a transverse section to enlarged scale through the cable joint substantially on line 5-5 of Figure l.

The same reference numerals are used throughout the figures to designate the same parts.

In cables of the type described, variations in the length o the insulated conductors resulting from changes in the cable tempera ture produce forces in the insulated conductors tending to cause relative longitudinal movement between the conductors and the pipe. The conductors are loosely enclosed by the pipe and ordinarily are free to snake within the pipe, except as they may be restrained by contact with other conductors in the pipe. The insulated conductors are not very flexible, and are drawn into the pipe in long lengths, usually more than a thousand feet. Where several conductors are enclosed Within a single pipe, as is usually the case, their relative positions in the pipe may vary along its length and therefore they will not all have the same freedom oi movement. For these and other reasons, the forces set up in the conductors will not be distributed uniformly in the :everal conductors, or uniformly throughout the length of any particular conductor and at any point along the cable the force tending to move a conductor longitudinally as the cable temperature changes may amount to many hundreds of Y pounds. Thev maximum forces may occur upon contraction of the conductor if cooled considerably below the temperature at the time of installation.

The forces set up in the conductors on expansion are largely limited by the shaking of the conductors within the pipe, but in some places this transverse movement of the conductors Within the pipe, in the absence of any holding means, may be accompanied by slight movement of the conductorslongitudinally of the pipe. The forces set up on contraction result in straightening and tensioning the conductors. Throughout much of the length of the cable this slight longitudinal movement of the conductors within the pipe probably is of no particular consequence, but if it occurs at a location Where it is desired to hold the insulated conductors against movement, it is likely to result in serious dam-age to the conductor insulation, or in damage to the holding means.

Joints in cables of the type described usually are semi-stop joints, that is, joints in which the now of the insulating duid from one of the pipe lengths to the connected pipelength is restricted to a small amount. This requires a barrier of some sort in the pipe With fluid-tight seals to the pipe Wall ,and to theinsulated conductor or con ductors. ln order'to avoid damage to the seals and to the conductor insulation it is desirable that there be no relative movement between the insulated conductors and the pipe atsuchasemi stop joint. y

A semi-stop in a pipe type',cable.'iisually,.als though not necessarily, is located at a cable joint.

In the usual semi-stop the insulated conductors pass through fairly close fitting openings ina bar rier plate extending across the pipe with its edge rigidly connected nuid tight relative tothe pipe. No particular problem .is encountered in providing .a seal between'the barrier plate and the pipe, or in securing the barrier plate against movement relative to the pipe. The insulated conductors are engaged by packing glands-Where they pass through the openings in the barrier plates and stufng boxesor the like .are provided for compressing the packingv glands about the in sulatedconductors. Each packing. gland oompresses `the conductor insulation to some extent around its entire circumference.; and serves not only v'to seal the opening through the barrier plate around the insulated conductor, but also to restrict the dow ofinsulating fluid longitudinally through the conductor insulation under the gland. lncables or the .type described, the conductors customarily .are individually insulated with .a multiplicity of over-lying helical Wrappings .of paper tape. Only a small tor-ce is required to slide the paper insulationfon the conductor in the absence of externally produced pressure of the insulation against-the conductor. rI f the conn ductor isto be heldagainst movement, the pres sure of the holding means must-be of such magnitude and .applied .to the. insulated conductor in such a -rnanner .as to prevent slipping between thev overf-lyinglayers of thepaper. insulation and also bet-Ween the paper and the conductor.

Prior tothe present invention, the packing gland ofthe .semi-stop aboveA describedhas been relied upon to hold the insulated v`conductor against movement. This has required increasing rthe pressure of the packing gland on the esterior of the conductorinsulation until the inner surfaceof the insulation gripped 'the conductor with sufdoientV pressure to holdY it against `the iorcestending .to niove` theconductor. This has meant pressiu-es. on .the insulation far beyond anything required merely` to .restrict the now of the duid insulation 1through the barrier plate opening to an acceptable amount, andthe conductor insulation has been seriously weakened.

For such-.a device to produce pressure on .the conductor under the insulation, the entire mass of insulation must be compressed. .Since the paper of the insulation is not elastic beyond an insignificant amount, the resulting gland pressure applied around the enti-re circumference of the insulated conductor produces sharp longitudinal creases in the'paper-bywhich the circumference of anylayer Vof paper adjusts itself te the smaller diameter to which it is compressed. These deep creases extend throughoutthe insulation on the conductor. .Of` course, .such .gland pressure cannot readily be. applied .over more thana very .short length .of .the cable, so that aside from the question .of damage to .theinsulation there are definite limitations on the ability of the circumferential holding device to restrain the cable longitudinally. For the reasons mentioned, the gland method is far from satisfactory for producing pressure on the conductor which will prevent slipping of the conductor under Vthe insulation.

According to the present invention, yclanlping means are provided for gripping the insulated conductors .rmly and Without impairment of the...electrical-insulation. This clamping means can be easily anchored to the pipe line to prevent Increment bet-veen the insulated conductors and thepipe. When used in a semi-stop joint, this clamping means may be applied either to the body of insulation built up over the connected conductor ends, orto the factor1 applied insulation .on one or the conductors adjacent the joint, or to both, and the clamping means may be anchored to the barrier plate. In such a `joint the packing gland is not called on to play any part in holding the `insulated conductor against longitudinal movement, Vand therefore the pres- 1 sure of the packing gland on the conductor insulation need be sufficient only to restrict .the

flow or insulatingv duid through 'the opening aroundthe conductor to an acceptable ngure.

The present invention will now be described particularly with reference to a semi-stop joint but it will be understood that the means for securing, an yinsulated .Conductor against movement .in the Acable pipe is not limited to use at the cable joints.

.Referring iirst to Figure vl of the drawings, pipes l l and l2, enclosing insulated conductors i3 and lll, respectively, are connected in end to end relation by means of the joint casing i5 .and the adapters it and il. Ordinarily the pipes, adapters and joint casing will be made ci steel, and the connections therebetween Will be Welded to insure a fluid tight and a mechanically strong connection.

Within the joint casing, near the ends thereof, are the barrier plates ES and i3, which `are made, for example, of bronze, and which cover the larger ends of the adapters i6 and Il respectively. The barrier plates are secured tightly against the ends or the adapters, as by means of cap screws t@ which pass through holes spaced around and near the edges of the barrier plates and engage threaded holes in the ends or" the adapters. Gaskets between the barrier plates and the adapters insure fluid tight connections.

The ends of the insulated conductors i3, or

which there are three in `the illustrative embodi-- ment, contained Within the 4pipe H passed through symmetrically spaced openings in the barrier plate lil into the joint easing l5. These openings in the barrier plate are slightly larger than the insulated conductors so as to permit threading the insulated conductors through the openings. Sind wires 22 applied over the insulated conductors at the factory to decrease the friction and to protect the insulation against damage while the conductors are being pulled into the pipe are suitably terminated short of the barrier plate, as shown.

Surrounding each insulated conductor i3 adjacent the barrier plate i3 is a packing gland 23, including gaskets, sleeve, follower, and means associated with the barrierplate for compressing the packing gland against the barrier plate and also against the conductor insulation around its entire circumference. Merely for .clarity in the drawings the `packing glands v are omitted in Figure 1, but are shown in Figure 2, which is an enlarged View of the left-hand portion of Figure l. In the illustrative embodiment, tightening the nuts on the studs 25, which are mounted in the barrier plate I8, will cause the follower 2t, to compress the gland gaskets against the barrier plate and against the conductor insulation. Thus, the packing glands will seal the openings in the barrier plate exteriorly of the insulated conductors i3 and, by reason of the pressure applied on the conductor insulation, will restrict the fiow oi insulating fluid longitudinally through the conductor insulation under the gland.

The pressure exerted by the packing gland on the conductor insulation should be sufficient to hold ba .z the pressure of the insulating iluid and to restrict the ilow of insulating fluid longitudinally through the conductor insulation to an acceptable ligure. Desirably this pressure should be several times the hydrostatic pressure being held back. Such a pressure on the conductor insulation may cause some creasing in the outer paper layers, perhaps to about one-half the depth of the insulation, but will not unduly weaken the insulation. For example, with a pressure on the fluid insulation contained within the cable of about 250 pounds per square inch, the pressure exerted by the packing gland on the insulation might be of the order of 1090 pounds per square inch. A still higher pressure is required to buckle the entire thickness of insulation of well-made paper insulated cable and only with such a buckling can the cable conductor be held firmly by the packing gland against slipping within the insulation.

While the barrier plate I9 at the other end of the joint casing might be omitted in some cases, ordinarily it is employed in a manner similar to the barrier plate l 8 for the purpose of restricting the flow of insulating fluid between the pipe i2 and the joint casing l5. The ends of the insulated conductors I4 contained within the pipe i2 pass through symmetrically arranged and fairly close :Fitting openings in the barrier plate lli into the joint casing I5. The skid wires 22 on the conductors i4 are terminated short of the barrier plate and each insulated conductor is surrounded by a packing gland 23 similar to those employed with the conductors I3 where they pass through the barrier plate IS.

Within the joint casing I5, the ends of corre spending conductors I3 and I4 are connected together and insulated in known manner. The insulation applied over each conductor joint may be built up to a somewhat larger diameter than the factory applied insulation on the conductor, although this is not necessarily so. The built-up insulation may be cylindrical in form for a distance and then taper down at both ends to the original conductor insulation, and such a construction is shown in the illustrative embodiment. Ordinarily the insulated conductors I3 and I4 will be shielded, and a shielding layer will be applied over the joint insulation between the shields on the two connected conductors.

According to the present invention, the insulated and shielded conductors are rmly gripped within the joint casing by an arrangement which grips the insulated conductors along narrow zones extending longitudinally of the conductors and spaced circumferentially around the conductors. The insulated conductor is gripped by a plurality of longitudinally extending strips, sometimes referred to hereinafter as strip grips,

which are pressed against the conductor insulation by enclosing clamping means.

The number of strip grips employed for holding each insulated conductor may vary, but there always will be at least two, and usually three or four. While the number used may be greater than four, there is comparatively little gain in gripping effect by the use of a larger number, and the gripping arrangement will be more difcult to manufacture and install. The strip grips desirably should be narrower than the spaces separating them, and their length, desirably not less than about three times their width, may be many times greater than the width. The strip grips may grip the conductors over the :factory applied insulation on the conductors, or over an insulated conductor joint, whether of the same diameter as the factory applied insulation I or of larger diameter, or over both.

In the illustrative embodiment there are four strip grips Z'I spaced uniformly around each insulated conductor. The distance between the strip grips, measured along the Outer surface of the insulated and shielded conduct-or, is about one and one-half times the width of a strip grip. The strip grips 21 are applied over the insulation, which has been built up over the conductor joint to a somewhat larger diameter than the original factory insulation, and extend for approximately the full length of the joint insulation. The edges of the joint insulation hidden by the strip grips in Figure 1 are shown in broken lines. The joint insulation tapers down at its ends to the factory applied insulation on the conductors, and wedge shaped insulating pieces 28 over these tapered portions build up the diameter under the strip grips to approximately the diameter at the central part of the insulate joint. These wedge shaped insulating pieces will be held in place against the tapered end portions of the built-up insulation by the pressure of the over-lying strip grips.

The strip grips desirably are made of nonmagnetic material, for example copper, While metal is preferred because of its strength, the strip grips may be made from strong insulating material, provided it does not contain any water. If the strip grips are made of metal, as in the illustrative embodiment, they preferably should be enclosed by thin insulating layers, for example a helical wrapping of papertape over each strip grip. Thin insulating strips 32 may also be employed between the strip grips and the enclosing clamps to further insulate these parts from each other. While it may be desirable to have all of the strip grips and their clamping means grounded, the purpose of the insulating coverings on the strip grips is to prevent electrica-l contact therebetween at undesired locations. In

this way, it will be possible to keep the losses from circulating currents which may be induced in the metallic parts of the gripping arrangement to a low figure.

The strip grips 2l spaced circumferentially around each insulated conductor are pressed and held rmly and resiliently against the insulated conductor by suitable clamping means. In the illustrative embodiment, a plurality of ring shaped metal clamps 29 are spaced longitudinally along each insulated conductor exteriorly of the strip grips. The clamps 29 are provided with radially disposed set screws 39 bearing against at least some of the strip grips to press them against the insulated conductor..

These clamps 29 should contain a certain amourant-roif.,springinesa;sozjahatl theyqLw-illzbe able f to follow up some;frelagationoigthe insulation on Wliichthe `stripsbear.;1 Theyemustlbe. .offsucient strength eso thatztheycwill contain-stresses- .e nature of; bezetting` In'lcinent. and r:Vet must.`

besuiciently flexible.: so-:that there will beV some. bending-that is" some distoriion.v ozthe ,ringsfas contrasted tosiniple tensile forces Whichzwoulrl 1 occur if: ,thetportionsz olffthe rings between they stringripswere simply-plane surfaces. v

is illustrated, -tthe clamps: 2 `are .substantially l.

circularin-.iorniand .should .-besuciently' elastic' to; permit increase-of f the .diameter at, the vthrusL bearings by a few thirty secondsofzan inch Wit-ha out-.permanentdistortionand to producev at the. Sametime thrust` against the stripsnofv the. re,

quired. pressure-to hold the conclanzton. OrgV nv etherfivords;the=.1ring.elamps. should bel/suffi;

qui.

oiently elastic sorthatrupon tightening the ct screws there will bean increase of several percent in the diameter of theV ring clampsalong i theaxisi otthe setscrews without permanent.

'lil

distortion of the clamps;` Desirably,-thisin'crease -f will heo'theorcler of threeperoent orrfnlore. 1

lin-"order: to obtain'uniorin distortion of `thel cable insulation it would beodesirable for each* ringclainp to have a set screw for each strip and fior the set screws all tobe brought up.

tension'successively by small increments. In la multiple conductor cableit isidiilicult jto use more than tivo setscrews.7 in a ring clamp because of i inaccessibility and. accordingly' the desired `arrangement involves the use ofv only two. set screws.

However, itis ydiiiicult to .obtain symmetrical die# tortion of the insulation with only the two screws per-clamp and it may bedesirable to tighten-th'e strip grips initially-` by the ,use-oi tempo rary tightening :nieanaffor example 't3 placed adjacenttothe rings, two-C clamps. foreachring.4

When these :o clamps` are .tightened up suceessivelyby. small increments; theresulting distortion or" the insulation is substantially -uniform, or, statedin anotherway, the distorted insulation is symmetricala'bout a plane passing. through the centerV of'. either pair :of` opposing strips. After .the strips have Abeen brought into il position withlthe required force by means of the C clamps, V'the setscrewsptll are then tightenedand the C clamps removed.`

By reference to Figure 4 ofthe drawings,- it will be seen that, when four strip grips arefused, the

conductor insulation becomes more or less squar ef with roundedcorners, incines-section.V If the ring clamps are placed in ,position ill-'st by'tighteningfthe `two set screws, theretends to be a greater -aniount ofI bulging Yof the insulation in;

o e quadrant ore-ne semi-circle ofv the insulated.

conductor than in the remaining portions. This would inean that for a given amount of compression there would be a greater distortion of the insulation than will be obtained Where thebulgingis divided evenly between the iourquadrants.

The strip grip can produce a high pressure per unit length or" the insulated conductor.Without creasing the paper, because the distortion lwhichl it produces is confined to a slight bending ofthe paper between the strip grips, Which does not damage 4the paper. Not only isthere a Ylacl; ci mechanical damage to the tapes, but thenc electrical damage; because the efectof the bensiing of the paper is simply ftoproduoe slight spaces between successive layers oi.: the ,papertape The arnount or" this separationis genera-llylessthan the separation.=,that.. existssbetweenxalimatntnp lgripsY approxi..

, and oneA end of the cable Was placedI in one pair; A

ofciawsr of; thetensile fmaehoeqand the asse bly 0i strip grins :,Wasyattaohed through a nc ins memberto the otherpair of jaws in the testing f machine.; Under these conditions and Withstr atelyfl inches long, a forcent.,- ligpoundsiwas required to sliclethe stripswith. respect tok the conductor of the cable,

After, or Ain sonle cases betorethestrip grips@ have beenclamped againstthe,` conductor yin- -sulation theygwill be;v anchoredrelative tn tlge cablegpipe orto the. jointcasingto insurethat therewiil be no movement of', the conductor-rele 'ative tothe pipe Conveniently thismay` bedone by connecting the eruisof` thestripgrips i in oner` end ofthe joint casingbybolts 33 to studs, which are,Y secured inthe barrierplate f lt. lt is suiiicientto holdthe-conductors if the strip 4grips'areanchored at only one endg Applicanthas pr vided means for firmly grip;Y ping and anchoring v insulated conductors relative to; thepipe in1v/blehtheyA are loosely en closedwithout damageto theV insulation.- It will be; evident that thestrip grips and :the associated Y clamps vWhich-press fthefstrip grips against the conductor insulation constitute a clamping means Whichfgrips'the insulated concluctor. The con-.- ductorsfwill be held against all forces which may develop therein tending to move;them duringsj operation of 'the cable.

The invention as herein described may bevari-r ously modied and embodied Within the scope ofthc subjoined clain'ls.

I claim:

l. In afcable system ofthetype in ru/'hichinsulated conductors-areloosely enclosed-by a pipe Whchsislled- Withfaninsulatingfluid under pressure, in combination, two lengths of insulat ed conductor connectedtogether in end to `end relation-with a Ybody of' insulation built up over ytheconductorconnection to larger diameter than the -original cable insulation and extending in both directions over the enclsof the original.in `sulation on the` connected conductors, theend.` portions of the built-up insulation tapering down to the original 'conductor insulation, a plurality of Vstrips,extending longitudinally of the insulated conductor joint and spaced circurnferentiallyl therearound, clamping means engaging the strips and vpressing them iirrnly against the insulated i ,conductor joint whereby the strips grip the in-` sulated conductor joint along narrow zones aced Vcircumferentially around the joint, said strips embracing the central'builtup portionoiI the insulation and extending bej/'ond'the ends thereofover vthe tapered portions of the insulationywedge shaped insulating vpieces underqthe;` ends of the strips, and held thereby in placeagainst/ thetapered end portions of thebuiltgup insulation-and meansl anchoring the strips -to therenclosine pipe-fio. prevent :Increment:Offfths insulated conductors relative` to the pipe at the -place of connection.

2. In a cable system of the type in which insulated conductors are loosely enclosed by a pipe which is filled with an insulating fluid under pressure, in combination, two lengths of insulated conductor connected together in end to end relation with a body of insulation covering the conductor connection, clamping means comp-ris- `ing a plurality of longitudinal strips spaced circumferentially around the insulated conductor connection, the said strips gripping the insulated conductor joint Iirmly along narrow zones spaced circumferentially around the joint, and means anchoring the strips to the enclosing pipe to prevent movement of the insulated conductors relative to the pipe at the place of connection.

3. In a cable system of the type in which insulated conductors are loosely enclosed by a pipe which is filled with an insulating iiuid under pressure, in combination, means for preventing movement of an insulated. conductor relative to the enclosing pipe comprising clamping means including a plurality of longitudinal strips, the

Asaid strips gripping the insulated conductor along narrow Zones spaced circumferentially around 'the conductor, and means anchoring the strips against movement relative to the pipe.

against the insulated conductor.

5. A cable system as described in claim 3, in which the longitudinal strips are spaced circumferentially around the insulated conductor, and in which there are a plurality of cooperating ring clamps spaced longitudinally along the conductor enclosing the strips, and radially disposed set screws in said ring clamps bearing against at least some of said strips, the said ring clamps and their set screws holding the strips pressed lrmly and resiliently against the insulated conductor.

6. A cable system as described in claim 3, in which the longitudinal strips are of non-magnetic, metallic material and are spaced circumferentially around the insulated conductor, and in which there are a plurality of clamps spaced longitudinally along the conductor pressing the strips firmly against the insulated conductor, and in which the strips are individually covered with thin layers oi insulating material.

7. A cable system as described in claim 3, in which the longitudinal strips are spaced circumerentially around the insulated conductor, and in which the clamping means includes a plurality of cooperating clamps spaced longitudinally along the conductor exteriorly of the strips to hold the strips pressed rmly and resiliently against the insulated conductor, characterized by the fact that the width of a strip is less than the spacing between strips and not more than about one third the length of the strip.

8. In a cable system of the type in which paper insulated cables are loosely enclosed by a pipe which is lled with an insulating fluid under pressure, in combination, a semi-stop to restrict flow of uid longitudinally in the pipe, said semistop comprising a barrier plate extending across the pipe and having its edge in fluid tight sealing association with the wall of the pipe, an opening in the barrier plate through which passes an insulated conductor, a packing gland surrounding the insulated conductor adjacent the barrier plate, means associated with the barrier plate to compress the packing gland against the barrier plate and about the insulated conductor substantially uniformly around its circumference, thus preventing flow of insulating iiuid through the opening in the barrier plate around the insulated conductor and substantially restricting flow of insulating uid longitudinally through the conductor insulation, clamping means comprising a plurality of longitudinal strips firmly gripping the insulated conductor adjacent the barrier plate in narrow zones spaced circumferentially around the conductor, and means anchoring the said clamping means to the barrier plate to prevent movement of the cable conductor relative to the packing gland and barrier plate.

9. A semi-stop joint for cables of the type in which an insulated conductor is loosely enclosed by a pipe lled with an insulating fluid under pressure comprising, in combination, a -joint casing connecting two pipe lengths, a barrier plate within the Joint casing near one end i thereof and connected adjacent its edge in iuid .ductor within the joint casing to the end of a conductor lying in the other pipe length, a body of insulation enclosing the connected conductor ends, clamping means comprising a plurality of longitudinal strips firmly gripping the insulated conductor which extends through the barrier plate in narrow zones spaced circumferentially around the conductor, and means anchoring the clamping means to the barrier plate to prevent movement of the insulated conductor where it passes through the barrier plate.

10. A semistop joint according to claim 9, in which a second barrier plate similar to the first one is disposed within the joint casing near the other end thereof for restricting substantially the flow of insulating fluid between the joint casing and the said other pipe length.

11. A semi-stop joint according to claim 9 in which the longitudinal strips extend lengthwise of the conductor joint and are spaced circumferentially therearound, and in which the clamping means includes a plurality of ring clamps enclosing the conductor joint over the strips, said ring clamps having radially disposed set screws bearing against at least some of the strips so that the pressure of the latter against the body of insulation may be adjusted.

12. A semi-stop joint according to claim 9, in which the longitudinal strips are of metal and extend lengthwise of the conductor joint, spaced circumferentially therearound, and in which the clamping means includes a plurality of metal clamps holding the strips pressed against the insulation, and in which a thin layer of electrical insulation separates each strip from the clamps.

13. A semi-stop joint for oil-impregnated, paper insulated cables loosely enclosed within a pipe I lled with an insulating duid under pressure comeageeeeee iii prising-g-` in combination, a'ointf'c'asi-ngfconnecting f two pipe' lengths,n ani-insulatedFioint'fwitliin said jointA casing connecting; 'aniiinsulat'edfcon'ductor 4in one pipe length 'toifan' 'insulatedA2 conductor'in the-ether pipelengthgharrier' 'means adjacent 'i one end ci thel jointlcasingcompressing the conduetor insulation against'the conductor around its "fciiemnference i and -suhstantiallyi Sres'tifict'ilng "iow foi" the insulating fluid-between the joint feasingI and Ione `01E the pipelengtlfisgiclainpingmeans comprising a 'plurality ofifongitndirial'strp's' :Hrm- .Aly gripping the insulated joint-'throughout afma- ";ority of its-'length in narrow -zonesxspacedfcirv1'cminiere-ntially arounfilthe joint, and'meanszfigid- 1: 'comprisingein 'Comoinatmml-:juintccasingcreonnecting two pipe lengths, aninsulatecliointfwth- "means-associatedWithieaid 'op'e'ning' and-exti'ng pressure -radiallyf inwa'dlyfonthe-I insulated *condu'ctor substantially uniformly aroun' itecic'ummeans to prevent movementoftheiinsulatedcon Lduotoli'elativefto the` loam-ier means.

f *14; a cable ,s-ystem 'off the Atype-"inf Whiehflinsulated conductors are loosely enclosedby# a'pipe "-presfme@ in combination; means y for preventing moveinentbf"ian'insulatedfeoneluetor ela'tive-to the pipe comprising leianiping means 'anchored to `the pipe Aand gripping`V thefinsulated conductor,

substantially r'the 'ow "'offv ins'uiating" fluid throigh the .openingin fthe"'liairierplataebutinsuicient to V'c1-ease the' vpapera'ns'iilation@enough to `produce conductor againstiongitdial movement' under plate t' hold 'the "conductor .'a'gaiiist" movement .relative t` the harrieijfpiate. M K

WJ. ATMNSGN.

@References-1 Gited-finithe .nient .this-patent "UNITEDfsTATEPATENTS vName K Date l: lia/iilne -J ;-Ap1.; v25, .-1933

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