LV12614B

LV12614B - Dead-end clamp for an insulated overhead cable, especially a bundleassembled overhead cable

Info

Publication number: LV12614B
Application number: LVP-00-122A
Authority: LV
Inventors: Esko TÖLKKÖ; Jarmo Harttunen
Original assignee: Ensto Sekko Oy
Priority date: 1999-09-16
Filing date: 2000-09-15
Publication date: 2001-05-20
Also published as: BG64407B1; BG104764A; PL201256B1; CZ20003361A3; LT4863B; RO121066B1; PL342442A1; FI19991965A; RU2597078C2; RU2597078C9; LV12614A; LT2000084A; AT500454A1; AT500454B8; FI107652B; AT500454B1; RU2233523C2; CZ298159B6; EE200000443A

Abstract

The invention relates to a dead-end clamp for an insulated overhead cable, especially a bundle-assembled overhead cable. Between metallic body plates (1,2) there are wedge-like plastic members (3,4), between which the ends of the wires of an ending cable are pressed by means of a clamp bolt (5). A lug (11,12) having an elongated locking hole (9) of variable width projects from both body plates (1,2). At the ends of the tension bail (6) made of stainless steel wire there is thickened section (7) which will fit through the locking holes (9) only at their wider end. The bail's (6) own tension presses the branches of the bail against the lugs (11,12).

Description

1 LV 12614

Dead-end clamp for an insulated overhead cable, especially a bundle-assembled overhead cable

The invention relates to a dead-end clamp for an insulated overhead cable, especially a bundle-assembled overhead cable, the dead-end clamp comprising two metallic body parts, between the body parts plastic parts having chute-formed sections for receiving the ends of the wires between the plastic parts, a clamp bolt for pressing the body parts and the plastic parts betvveen them tovvards each other to lock the ends of the wires betvveen the plastic parts, and a tension bail incorporated in the clamp, by means of vvhich the clamp can be made to grip onto a hook or other fastener on a wall or pole.

In this type of dead-end clamps previously used by the Applicant, plastic parts are moulded around the ends of the bail, for vvhich plastic parts there are receiving spaces in the body. This arrangement is suitable for use with small tension loads, for example, for connecting one small-diameter wire. With thicker, multiple-pole vvires the Applicant has used, as a dead-end clamp, a solution in vvhich the ends of the tension bail are moulded over a long distance inside a plastic part vvhich is placed in the space betvveen the body parts over the entire length of the body. This arrangement increases the thickness of the clamp, in addition to vvhich the bail with the fastening members moulded around it constitutes an expensive component.

In addition to the foregoing, previously is also knovvn the type of dead-end clamp in vvhich the body consists of two vvedge parts vvithin each other, in the space betvveen vvhich the end of a single cable is vvedged. The bail is made of stainless Steel vvire, both ends of vvhich attach to holes at the projecting end of one of the vvedge parts. This dead-end clamp is also suitable for fastening the end of a single cable. By using stainless Steel vvire is achieved the advantage that the dead-end clamp vvill be applicable for use in environments susceptible to corrosion. 2

The object of the invention is to provide a dead-end clamp vvhich is suitable for a multi-core cable (typically 2-4 cores) and in vvhich the mutual attachment of the body and the bail is solved in a simple and economical manner.

This object is achieved by means of the invention, on the basis of the characteristics disclosed in claim 1.

The dependent claims describe preferred embodiments of the invention.

Two embodiments of the invention are described in greater detail in the follovving, with reference to the appended dravvings in vvhich

Figurēs 1, 2 and 3 shovv a dead-end clamp relating to the first embodiment of the invention, as seen from the side, from the rear and from above;

Figurēs 4 and 5 shovv a dead-end clamp relating to the second embodiment of the invention, as seen from the side and from the rear (the top vievv corresponding to Figurē 3);

Figurē 6 shovvs the lovver body plate 2 of the dead-end clamp on a larger scale, as seen from the side, the plate being applicable for use in both embodiments;

Figurēs 7 and 8 shovv plastic parts 3, 4 applicable for use in both embodiments, as a partial section and as seen from the inner side; and

Figurē 9 shovvs the third plastic part 14 used in the embodiment shovvn in Figurēs 4 and 5 on a larger scale and in partial cross-section (the upper plān vievv corresponding to Figurē 8 and the lovver plān vievv deviating from it only in that the collar 17 and the recess 18 have changed places. The baffle plates 20 shovvn in Figurē 8 for 3 LV 12614 increasing creeping resistance along the surface betvveen the ends of the wires and the mētai body are not needed in the middle plastic part 14).

The dead-end clamp according to both embodiments comprises two metallic body parts 1, 2, betvveen vvhich are plastic parts 3, 4, having chute-formed sectionslO for receiving the ends (not shovvn) of the vvires betvveen the plastic parts 3, 4 or betvveen the plastic parts 3,14, 4. The embodiment shovvn in Figurēs 1 to 3 is suitable for čabies vvith tvvo vvires and the embodiment shovvn in Figurēs 4, 5 is suitable for čabies vvith three or four vvires. The clamp bolt passes through the body parts 1, 2 and the plastic parts 3, 4 (and possibly 14) betvveen them in order to press the parts tovvards each other, to clamp the ends of the vvires betvveen the plastic parts. By means of the tension bail 6 the clamp can be made to grip onto a hook or other fastener on a wall or pole.

From both body parts 1, 2 projects a bail 6 lug 11,12 having an elongated locking hole 9 of variable vvidth. In the case shovvn, the lūgs 11,12 are direct extensions of the plate-like body parts 1, 2 and have keyhole-shaped locking holes 9, the narrovver end of vvhich points tovvards the outer end of the lug. At the ends of both branches of the tension bail 6 are thickened sections 7 vvhich are dimensioned in such a way vvith respect to the locking holes 9 that they vvill fit through the locking holes 9 only at their vvider end. The bail’s 6 ovvn tension presses the branches of the bail against the inner surfaces of the lūgs 11,12, whereby the bail 6 does not turn on account of its ovvn vveight, but remains in the position into vvhich it has been turned by using force, typically in the position shovvn in Figurē 3, parallel vvith the ends of the cable.

The lūgs 11,12 have recesses 13 (Fig. 6) for receiving the thickened sections 7 of the ends of the bail in the area of the narrovver end of the locking holes 9.

The lūgs 11, 12, recesses 13 and locking holes 9 are located and designed in such a way vvith respect to each other that in the dead-end clamp assembled into a State of readiness, the bail 6 cannot be detached from its place. When the clamp bolt 5 is detached, the body parts 1, 2 can be turned in such a way that the thickened end sections 7 of the bail 6 can be slipped into place or be 4 removed from their place by moving the thickened section 7 over the edge of the recess 13 to the wider end of the hole 9 from where it can pass through the hole. 5 In the cases described, the end bendings 8 of the bail 6 have been made in such a way that the ends of the bail are directed away from each other. They could, alternatively, be directed tovvards each other, in which case the ends of the branches of the bail 6 would rest against the outer sides of the lūgs 11, 12. Furthermore, it is also possible for the ends of the bail 6 to be straight vvithout 10 any bendings 8, in vvhich case the lūgs 11,12 would be provided vvith the necessary parts designed for gripping, or bendings.

In both embodiments, the plastic parts 3, 4 resting against the body parts 1, 2 are wedge-like in the direction of pulling of the dead-end clamp in such a way 15 that the plastic parts 3, 4 expand tovvards the tension bail 6. The through holes 16 of the clamp bolt in the plastic parts 3, 4 and in the possible third plastic part 14 are elongated in the direction of pulling. Ali through holes 16 in the plastic parts 3, 4, 14 have transverse necks 19 vvhich keep the clamp bolt 5 at one end of the through hole 16 until the neck 19 breaks due to the effect of the clamping 20 force and allovvs the body parts 1,2 to slide tovvards the thicker end of the vvedge-like plastic parts 3,4. In addition to this vvedge effect, gripping can be made more efficient by transverse grooving or cogging of the chutes 10. The third plastic part 14 betvveen the plastic parts 3, 4 comprises tvvo chute-formed sections 10 on either of the opposite surfaces. 25

Each of the plastic parts 3, 4, 14, comprises a projecting collar 17 on one side of the through hole 16 of the clamp bolt, and on the opposite side of the hole, at the corresponding point, a recess 18 vvhich receives the collar 17 of the adjacent plastic part. Therefore, in the plastic parts 3,4,14 that are on top of 30 one another, the collars 17 together form creeping resistance betvveen the ends of the vvires entering into the chutes 10 and the bolt entering into the hole 16.

At the same time, the plastic parts 3, 14, 4 are guided into a position opposite each other in the correct position. 5 LV 12614

With the dead-end clamp structure described, as a tension bail 6 can be used single-thread stainless Steel wire vvhich is durable also in surroundings susceptible to corrosion.

In the embodiments described, the body parts and the plastic parts are joined together by means of one clamp bolt 5, the thread of vvhich is in contact with the threaded hole 15 (Figurē 6) of one body part 2, and the head of vvhich is pressed against the other body part 1. Naturally, parts that are longer in the direction of pulling and two successive clamp bolts 5 can also be used.

As seen in Figurēs 7 to 9, especially in Figurē 8, at the bottom of the chute-formed sections 10 are transverse curved or V-shaped grooves, the planē of curvature or V-plane of vvhich is inclined in the longitudinal direction of the chute and forms a sharp angle with the normai planē perpendicular to the longitudinal axis of the chute. The edges of the grooves are sharp for forming ” gripping cogging, and the depth of the grooves decreases vvhen moving from the centre of the chute 10 tovvards the edges of the chute.

The concave side edge of the grooves or the inside edge of the V-shape is on the side of the tension bail (in Figurē 8 on the side of the baffle plates 20), vvhich means that these edges vvill receive the pulling force directed at them by the wire. The surface material of the wire then vvedges tovvards the Central area, that is, the bottom of the chutes 10 and penetrates vvith pressure inside the grooves. This, together vvith the lengthening of the gripping line of the grooves, brings about a substantially better hold than the vertical grooves vvhich are located on the normai planē perpendicular to the longitudinal axis of the chute. The sharp angle betvveen the planē of curvature of the grooves and the normai planē of the chute is preferably vvithin the range from 30 to 50°, most preferably about 45°. The grooves can be made, for example, by milling, by inclining the milling tool to a position corresponding to the said angle. 6 LV 12614

Claims 1. A dead-end clamp for an insulated overhead cable, especially a bundle-assembled overhead cable, the dead-end clamp comprising two metallic body parts (1,2), betvveen the body parts plastic parts (3, 4) having chute-formed sections (10) for receiving the ends of the wires betvveen the plastic parts (3,4), a clamp bolt (5) for pressing the body parts and the plastic parts betvveen them tovvards each other to lock the ends of the vvires betvveen the plastic parts, and a tension bail (6) incorporated in the clamp, by means of vvhich the clamp can be made to grip onto a hook or other fastener on a vvall or pole, characterised in that from both body parts (1, 2) projects a bail (6) lug (11,12) having an elongated locking hole (9) of variable vvidth, that at the ends of both branches of the tension bail (6) are thickened sections (7) vvhich are dimensioned in such a way vvith respect to the locking holes (9) that they vvill fit through the locking holes (9) only at their vvider end, and that the bail’s (6) ovvn tension presses the branches of the bail against the lūgs (11,12). 2. A dead-end clamp as claimed in claim 1, characterised in that the locking holes (9) narrovv tovvards the outer ends of the lūgs (11,12), and that the ends of the branches of the bail (6) are bent to direct the ends away from each other or tovvards each other. 3. A dead-end clamp as claimed in claim 1 or 2, characterised in that the plastic parts (3, 4) resting against the body parts (1,2) are vvedge-like in the direction of pulling of the dead-end clamp in such a way that the plastic parts (3,4) expand tovvards the tension bail (6), and that the through hole (16) of the clamp bolt (5) is elongated in the direction of pulling. 4. A dead-end clamp as claimed in any of the claims 1 to 3, characterised in that the body parts (1, 2) and the plastic parts (3, 4) are joined together by means of one clamp bolt (5), the thread of vvhich is in contact vvith the threaded hole (15) of one body part (2), and the head pressed against the other body part (1). 7 5. A dead-end clamp as claimed in any of the claims 1 to 4, characterised in that on one side of the hole (16) provided in the plastic part (3, 4) for the passing through of the clamp bolt (5) is a projecting collar (17), and on the opposite side of the hole (16), at the corresponding point, is a recess (18) which receives the collar (17) of the adjacent plastic part. 6. A dead-end clamp as claimed in claim 1 or 2, characterised in that the tension bail (6) is a single-thread stainless Steel wire. 7. A dead-end clamp as claimed in any of the claims 1 to 6, characterised in that between the two plastic parts (3, 4) is a third plastic part (14), on both of the opposite sides of which are two chute-formed sections (10) and betvveen them a hole (16) elongated in the direction of pulling for the passing through of the clamp bolt (5). 8. A dead-end clamp as claimed in claim 3 or 7, characterised in that there is a transverse neck (19) in the through hole (16) of the clamp bolt, which neck keeps the clamp bolt (5) at one end of the through hole (16) until the neck (19) breaks due to the effect of the clamping force and allovvs the body parts (1, 2) to slide tovvards the thicker end of the wedge-like plastic parts (3, 4). 9. A dead-end clamp as claimed in claim 1, 2 or 6, characterised in that the lūgs (11,12) have recesses (13) for receiving the thickened sections (7) of the ends of the bail in the area of the narrower end of the locking holes (9), and that the lūgs (11, 12), recesses (13) and locking holes (9) are located and designed in such a way with respect to each other that in the dead-end clamp assembled into a state of readiness, the bail (6) cannot be detached from its place. 10. A dead-end clamp as claimed in any of the claims 1 to 9, characterised in that at the bottom of the chute-formed sections (10) are transverse curved or V-shaped grooves, the planē of curvature or V-plane of vvhich is inclined in the longitudinal direction of the chute and forms a sharp angle with the normai planē perpendicular to the longitudinal axis of the chute. 8 LV 12614 11. A dead-end clamp as claimed in claim 10, characterised in that the edges of the grooves are Sharp for formirig gripping cogging and that the depth of the grooves decreases when moving from the centre of the chute (10) tovvards the edges of the chute. 5 12. A dead-end clamp as claimed in claim 10 or 11, characterised in that the concave side edge of the grooves or the inside edge of the V-shape is on the side of the tension bail (6) and receives the pulling force directed at it by the wire. 10 13. A dead-end clamp as claimed in any of the claims 10 to 12, characterised in that the Sharp angle betvveen the planē of curvature of the grooves and the normai planē of the chute (10) is within the range from 30 to 50°, most preferably about45°. LV 12614 9 (57) Abstract

The invention relates to a dead-end clamp for an insulated overhead cable, especially a bundle-assembled overhead cable. Betvveen metallic body plates (1, 2) are wedge-like plastic members (3, 4), between which the ends of the 5 wires of an ending cable are pressed by means of a clamp bolt (5). From both body plates (1, 2) projects a lug (11,12) having an elongated locking hole (9) of variable width. At the ends of the tension bail (6) made of stainless Steel wire are thickened sections (7) which will fit through the locking holes (9) only at their wider end. The bail’s (6) own tension presses the branches of the bail against the lūgs (11, 12). 10

Claims

LV 12614 IZGUDROJUMA FORMULA Spriegošanas spaile izolētam virszemes kabelim, īpaši grīstveida virszemes kabelim, kas satur divas metāliskas korpusa da|as (1, 2), starp korpusa da|ām esošas plastmasas daļas (3, 4), kurām ir renveida zonas (10) vadu galu ievietošanai starp plastiskajām daļām (3, 4), iespīlēšanas skrūvi (5) korpusa daļu un attiecīgo plastmasas daļu starp tām saspiešanai vienai attiecībā pret otru, lai ieslēgtu vadu galus starp plastmasas daļām, un satur spailē iemontētu nospriegošanas skavu (6), ar kuras palīdzību spaile var tikt uzkabināta uz satvērējāķa vai cita nostiprināšanas līdzekļa sienā vai stabā, raksturīga ar to, ka no abām korpusa daļām (1,2) izvirzās skavas (6) montāžas austiņas (11, 12), kam ir mainīga platuma izstiepta slēgatvere (9), ka nospriegošanas skavas (6) abu zaru galos ir biezākas zonas (7), kuru izmēri attiecībā pret slēgatverēm (9) ir tādi, ka tās var tikt salāgoti caur slēgatverēm tikai to platākajā galā, un ar to, ka skavas (6) pašnospriegojums spiež skavas zarus pret montāžas austiņām (11,12). Spriegošanas spaile saskaņā ar 1. punktu, kas raksturīga ar to, ka slēgatveres (9) sašaurinās virzienā uz montāžas austiņu (11, 12) ārdiem galiem, un ka skavas (6) zaru gali ir saliekti, lai vērstu galus prom vienu no otra vai vienu otram pretī. Spriegošanas spaile saskaņā ar 1. vai 2. punktu, kas raksturīga ar to, ka plastmasas daļas (3,4), kas balstās uz korpusa daļām (1,2), spriegošanas spailes vilkšanas virzienā ir ķīļveidīgas tādā veidā, ka plastmasas daļas (3, 4) paplašinās virzienā uz nospriegošanas skavu (6), un ka iespīlēšanas skrūves (5) caurums (16) vilkšanas virzienā ir iegarens. Spriegošanas spaile saskaņā ar jebkuru punktu no 1. līdz 3. punktam, kas raksturīga ar to, ka korpusa daļas (1, 2) un plastmasas daļas (3, 4) ir savienotas kopā ar iespīlēšanas skrūves (5) palīdzību, kuras vītne ir saskarē ar vienas korpusa daļas (2) vītņoto caurumu (15) un ar otrai korpusa daļai (1) piespiestu galviņu. 2EN 12614 DESCRIPTION OF THE INVENTION Tensioning clamp for an insulated surface cable, in particular for a sloped surface cable containing two metallic body parts (1, 2), between plastic parts (3, 4) of the body parts having a groove area (10) for inserting the ends of the wires between the plastic parts (3, 4), the clamping screw (5) for compressing the body part and the respective plastic part between them relative to each other to engage the ends of the wires between the plastic parts and comprising a tensioning clamp (6) mounted on the terminal, by means of which the clamp can be hooked onto a grab or other fastening means in a wall or pillar, characterized in that clamps (6, 11) of clamps (6) protrude from both parts of the housing (1,2) having a variable width stretched shutoff ( 9) that the tensioning clamps (6) at both ends of the tines have thicker areas (7), the dimensions of which with respect to the closures (9) are such that they can be aligned through the closure. m only at their widest end, and with the clamp (6) self-tensioning clamping the clamp bands against the mounting headset (11,12). A tensioning clamp according to claim 1, characterized in that the closing plugs (9) taper towards the ends of the mounting head (11, 12), and that the tongue ends of the clamps (6) are bent to direct the ends away from each other or facing each other. A tensioning clamp according to claim 1 or 2, characterized in that the tensioning clamps of the plastic parts (3,4) on the body parts (1,2) are wedge-shaped in the direction of towing such that the plastic parts (3) 4) extend towards the tensioning clamp (6), and the hole (16) of the clamping screw (5) is oblong in the direction of towing. Tensioning clamp according to any one of claims 1 to 3, characterized in that the body parts (1, 2) and the plastic parts (3, 4) are connected together by a clamping screw (5), the thread of which is in contact. with a threaded hole (15) of one housing part (2) and a head pressed against the other body part (1). 2

5. Spriegošanas spaile saskaņā ar jebkuru punktu no 1. līdz 4. punktam, kas raksturīga ar to, ka cauruma (16), kas ir izveidots plastmasas da|ā (3, 4) iespilēšanas skrūves (5) cauriešanai, vienā pusē ir gredzenveida izvirzījums (17) un cauruma (16) otrā pusē atbilstošā vietā ir dobums (18), 5 kas uzņem blakus esošās plastmasas dajas izvirzījumu (17).5. A tensioning clamp as claimed in any one of claims 1 to 4, characterized in that the hole (16) formed in the plastic part (3, 4) for penetrating the screw (5) has a ring-shaped seal on one side. the protrusion (17) and the cavity (18) 5 on the other side of the hole (16) receive a projection (17) of the adjacent plastic tray.

6. Spriegošanas spaile saskaņā ar 1. vai 2. punktu, kas raksturīga ar to, ka nospriegošanas skava (6) ir nerūsošā tērauda viendzīslas vads.A tensioning clamp according to claim 1 or 2, characterized in that the tensioning clamp (6) is a stainless steel monofilament wire.

7. Spriegošanas spaile saskaņā ar jebkuru punktu no 1. līdz 6. punktam, kas raksturīga ar to, ka starp divām plastmasas daļām (3, 4) ir trešā plastmasas daļa (14), kuras abās pretējās pusēs ir divas renveida zonas (10) un starp tām ir caurums (16) iespilēšanas skrūves (5) cauriešanai, kas ir iegarens vilkšanas virzienā. 157. A tensioning clamp as claimed in any one of claims 1 to 6, characterized in that between the two plastic parts (3, 4) there is a third plastic part (14) having two annular zones (10) on both opposite sides. and there is a hole (16) between them for penetrating the clamping screw (5), which is oblong in the pulling direction. 15

8. Spriegošanas spaile saskaņā ar 3. vai 7. punktu, kas raksturīga ar to, ka iespilēšanas skrūves caurumā (16) šķērsvirzienā ir kakliņš (19), pie kam šis kakliņš notur iespilēšanas skrūvi (5) cauruma (16) vienā galā, līdz kakliņš (19) iespilēšanas spēka darbības rezultātā lūzt un ļauj korpusa daļām (1,2) 20 slīdēt virzienā uz ķīļveidīgo plastmasas daļu (3,4) biezāko galu.8. A tensioning clamp according to claim 3 or 7, characterized in that the clamping screw hole (16) in the transverse direction has a nose (19), the neck of which holds the clamping screw (5) at one end of the hole (16) until the neck (19) breaks as a result of the action of the clamping force and allows the body parts (1,2) 20 to slide towards the thickest end of the wedge-shaped plastic parts (3,4).

9. Spriegošanas spaile saskaņā ar 1., 2. vai 6. punktu, kas raksturīga arto, ka montāžas austiņām (11, 12) ir padziļinājumi (13) nospriegošanas skavas galu biezāko zonu (7) ievietošanai slēgatveru (9) šaurākā gala zonā 25 un ka montāžas austiņas (11, 12), padziļinājumi (13) un slēgatveres (9) ir izvietotas un konstruētas attiecībā cits pret citu tādā veidā, ka spriegošanas spailē, kas samontēta gatavības stāvoklī, skava (6) nevar tikt atdalīta no savas vietas.9. A tensioning clamp according to claim 1, 2 or 6, characterized in that the mounting headphones (11, 12) have recesses (13) for inserting the thickest areas (7) of the ends of the tensioning clamp into the narrower end zone 25 of the closing screws (9) and that the mounting headphones (11, 12), the recesses (13) and the locking plugs (9) are arranged and constructed relative to each other in such a way that the clamp (6) cannot be detached from its position in the tensioning clamp mounted in the ready state.

10. Spriegošanas spaile saskaņā ar jebkuru punktu no 1. līdz 9. punktam, kas raksturīga ar to, ka renveida zonas (10) ir šķērsvirzienā izliektas vai V-veida rievas, kuru liekuma plakne vai V-plakne renes garenvirzienā ir slīpa un veido šauru leņķi ar normāiplakni, kas ir perpendikulāra renes garenasij.10. A tensioning clamp according to any one of claims 1 to 9, characterized in that the groove areas (10) are curved or V-shaped in the transverse direction, the curvature plane or V-plane of which is sloped longitudinally and forms narrow angles with the normal plane perpendicular to the longitudinal axis of the groove.

11. Spriegošanas spaile saskaņā ar 10. punktu, kas raksturīga ar to, ka rievu malas ir asas, lai radītu sprūdsatvērienu, un ka rievu dziļums samazinās virzienā no renes (10) centra uz renes malām. 3 LV 1261411. A tensioning clamp according to claim 10, characterized in that the edges of the grooves are sharp to create a clamping grip, and that the depth of the grooves decreases in the direction of the center of the groove (10) on the edges of the ridge. 3 LV 12614

12. Spriegošanas spaile saskaņā ar 10. vai 11. punktu, kas raksturīga ar to, ka ieliektā rievu sānu mala vai V-formas iekšmala ir nospriegošanas skavas (6) pusē un uzņem uz to vērsto vilces spēku, ko rada vads.12. A tensioning clamp according to claim 10 or 11, characterized in that the concave groove side edge or the V-shaped inner edge is on the side of the tensioning clamps (6) and receives the traction force exerted on it by the wire.

13. Spriegošanas spaile saskaņā ar jebkuru punktu no 10. līdz 12. punktam, kas raksturīga ar to, ka šaurais leņķis starp rievu liekuma plakni un renes (10) normālplakni ir robežās no 30 līdz 50°, vislabāk - apmēram 45°.A tensioning clamp according to any one of claims 10 to 12, characterized in that the narrow angle between the groove bending plane and the normal plane of the groove (10) is between 30 and 50 °, preferably about 45 °.