FR2529021A1 - Controlled pressure screw-down type clamping cable connector - has toothed anvil and shoe for gripping insulated cables and has threaded disc which limits movement of screw - Google Patents

Abstract

The principle lies in limiting the travel of the shoe of a screw-tightened clamp to a reset amount which ensures the correct degree of pressure or deformation. The operation of the clamp is insensitive to mfg. tolerances and needs no adjustment after setting up. The cable to be clamped (16) usually carries an insulating layer (17). It is positioned on a toothed anvil (8) and is held by a movable toothed shoe (7). The shoe is held against the cable by the pressure of a spiral spring (21) which bears against the upper arm (1b) of the yoke (1). A rectangular plate (5) has a threaded hole (10) and is prevented from rotating. Downward movement is imparted to the shoe via the end of a bolt (2) which is screwed progressively down through the plate. The bolt has a threaded disc (4) which can be preset at any position along its length and then prevented from further rotation. When the bolt is screwed down, the shoe is forced into the cable, the pointed sections (7) to penetrate the insulation and become embedded in the conducting core. Once the disc (4) reaches the rectangular plate (5), further rotation is prevented and the clamping pressure is maintained at its final value, even in the presence of vibration.

Description

 The present invention relates to a tightening device of the screw / nut type, hereinafter called a "clamp", with controlled stroke for clamping a part between a bearing heel secured to a nut part and a clamping heel. arranged at the end of a screw part, in particular for electrical connectors with insulation perforation.

 We already know, in the field of the controlled amplitude of a clamping system by screw and nut of the clamp type, several types of devices which can fall into two main categories.

 In a first category, the stop of the tightening, therefore of the screw / nut "stroke", is obtained by limiting the tightening torque to a predetermined value, either by means of a torque wrench with elastic mechanical deformation or with electronic indication at from information coming from a deformable element on which are applied, for example, strain gauges (French patent application filed by the Applicant under NO 80 27898 on 12/31/1980) or by failure, at a predetermined value of the tightening torque, of a "breakable" part of the tightening opinion.

In a second category, the tightening stop is obtained by means of a mechanical device interposed between the screw and nut parts, ensuring either slippage between two portions of the screw part by a friction system, or a "disengagement of the system screw / nut by escaping the screw from its nut, the latter effect being obtainable, for example, by interrupting, in a determined zone, the threading of the screw which then comprises a smooth part of diameter less than the diameter on the thread of said screw0
The drawbacks of these systems essentially lie in their relative imprecision due, to the very principle of their design, to the lack of rigor in their industrial production in large series, to mechanical or electrical aging of their components, or even to parasitic constraints, superimposed on pure torsion, introduced unconsciously by the operator when he implements, without special and restrictive precautions, an ordinary tool such as in general a simple ordinary tightening wrench.

 A control of the tightening stroke of a screw in a clamp, vice, nut is very particularly sought during the use of electrical connectors with insulation perforation for the purpose of derivation from insulated cables with core metallic, wired or massive, overhead power distribution or transmission lines.

 As we know, when using this technique on new buildings or for repair work, it is a question of obtaining, thanks to the teeth or the sharp blades of the socket which constitute the essential organs of the connector, an electrical contact with the metallic core which, after perforation of the insulating sheath is "sufficient" to ensure the transfer of a large current intensity without however seriously damaging the conductive metallic core, particularly fragile in its constituent strands when said core is wired.

 It is therefore understandable how the systems for limiting the tightening torque known to date very imperfectly solve the problem posed by the use of such connectors and in fact constitute only an appearance of solution, owing to the differences in hardness of the insulating sheaths resulting from the plurality of materials which constitute them, from differences in the use of the same material between the various cable manufacturers, from the aging state of the insulation of cables exposed to atmospheric agents which generally results by a hardening progressively over time, finally and above all by the very significant variations in the hardness of the insulation as a function of the temperature (winter or summer, heating due to the operating current of the conductor).

 More specifically to these bypass operations, it is already known, when implementing a connector, to first identify the establishment of a contact "stricto sensu" between the teeth of the gripping members. current of the connector and the metallic core of the cable thanks to the appearance of an acoustic or light signal; the latter originates from said contact which, by electronically amplified capacitive effect, triggers said signal, the entire system forming part of an electronic tightening key as described in the French patent application of the Applicant filed on 18 / 04/1977 under the NO 77 11550 and published under the NO 2.387.739. In a second time, one causes mechanically, after perception of the contact signal ", a more" deep "contact capable of ensuring the transfer of '' an appropriate current intensity; for this purpose the teeth of the connector current-taking members are penetrated by a determined value into the metallic core of the cable by instructing the user to perform, after perception of said contact signal, a predetermined number of turns or fractions of turns of the connector tightening screw. Said tightening screw having a well determined pitch, the application of the above-mentioned instruction causes "ipso facto" the desired penetration dtes d cuts in the conductive core.

 This technique virtually eliminates the serious drawbacks previously mentioned with regard to the application to insulation piercing connectors of known devices with controlled travel or torque. However, it should be noted that under the often difficult conditions for implementing connectors on overhead electrical networks using insulated cables, it is restricting, even inconvenient and difficult to strictly apply the setpoint for the number of turns of the screw. to be carried out after perception of the "contacting" signal.

 The present invention aims to overcome the drawbacks specific to electrical bypass connectors, as well as, more generally, those presented by the controlled stroke tightening devices known to date.

The invention proposes for this purpose a device for clamping a part, of the clamp type with controlled stroke for clamping the part between a support shoe secured to a nut part and a clamping shoe disposed at the end. a screw, in particular for an electrical connector with insulation perforation, characterized by the mounting with clearance of the clamping shoe and a nut plate immobilized in rotation relative to the nut part on an axial extension of the screw , and by associating with the screw a collar immobilized thereon, at a predetermined distance from said end of the viso
A device according to the invention has the double advantage of supporting, by its remarkable simplicity of structure, industrial mass production, while leading, despite its remarkable ease of implementation, to a mechanical and positive control (this is that is to say rigorous) of the amplitude of the tightening applied to its screw part from the moment when its tightening heel, perforating or not, comes into contact with the part to be tightened applied against its supporting heel, perforating or no. It should be noted that said part to be clamped undergoes, in addition to a possible partial perforation, a certain deformation by crushing, in particular in the case of elastomer objects or hollow bodies made of plastic or even metallic material, or also of insulated metallic cables. .

 The invention naturally relates very particularly to connectors designed according to the structure of the aforementioned clamping devices.

The objects, characteristics and advantages of the invention appear moreover from the description which follows, given by way of nonlimiting example, with reference to the appended drawings in which
Figure 1 is an elevational view with partial cutaway of an electrical bypass connector according to the invention before tightening
Figure 2 is a section along line II-II of the connector according to Figure 1
Figure 3 is an elevational view of said connector, its clamping shoe being in contact with the cable to be clamped
Figure 4 is an elevational view of said clamping "bottom" connector
Figure 5 is an elevational view of said connector after complete loosening.

 In the embodiment illustrated by FIGS. 1 to 5, a clamping device, according to the invention, for an electrical connector for implantation bypass, comprises a metallic conductive body 1, in the shape of a U with a middle part la and two small branches lb and lco Thanks to a tapped hole 3 formed in one of its small branches lb, this conductive body 1 serves as a nut part vis-à-vis a pressure or tightening screw 2, at a so-called active end of which is mounted with axial clearance a pressure or clamping shoe 7 opposite a shoe or support heel 8 carried by the other small branch lc of the body 1. The shoes 7 and 8 have teeth or sharp blades 13 and 14 adapted to cooperate with a view to enclosing with perforation, in two diametrically opposite zones, a main cable 17 whose conductive metal core 16 is protected by an insulator 15. The body 1 also comprises a channel 18 into which is introduced a end, stripped as shown in the fi gures l to 5, of a branch cable 20 which is held there by means of a pressure screw 19, perforating or not equipped or not with the device according to the invention.

 According to the invention, the clamping device that constitutes the connector of FIGS. 1 to 5 further comprises on its screw 2, a flange 4 immobilized relative to this, as well as a nut plate S immobilized in rotation relative to the body. 1 forming a nut.

 The collar 4, shown in FIGS. 1 to 5 with an annular shape, projects radially with respect to the screw 2.

 The axial clearance of the pressure shoe 7 at the end of the screw is obtained by mounting it on a smooth axial extension 9 of the screw. As shown in Figures 1 to 5, this extension is advantageously constituted by a smooth stud ensuring by a development 6 of its free end a rotary crimping of the shoe 7 on the screw.

 The nut plate 5 is mounted on the screw 2 between the pressure shoe 7 and the fixed flange 4, by means of a tapped hole 10. Its thickness e is less than the axial clearance allocated to the shoe 7, so that , depending on the case, this plate may or may not be engaged on the threads of screw 2.

The nut plate 5 is immobilized in rotation relative to the body 1 forming a nut by confrontation, with the possibility of axial sliding, of a portion 11 of its axial section, not coaxial with the screw 2, against an axial surface 12 of the the part of the body 1, the profile of which, perpendicular to the screw 2, is at least partially complementary to that of said portion ll.

 In the embodiment shown in Figures 1 to 5, the nut plate 5 has a substantially rectangular profile, the portion ll of its edge being planar, as well as the axial surface 12 of the body 1. For reasons which will appear more far away, it is advantageously kept in contact with the pressure shoe 7 under the action of a return member 21, such as a spiral spring, working in compression and bearing under the small threaded branch 16 of the body 1, and suitable for playing without contact with the fixed flange 4. A chamfer 22 is also advantageously formed at the active end of the screw 2 to facilitate its engagement in the wafer 5. A reverse arrangement would render the same services.

 In the arrangement of the connector shown in Figure 1, the cable 17 rests without penetration on the teeth 14 of the support shoe 8, without contact with the teeth 13 of the pressure shoe 7. Such a position is obtained for example under the effect of gravity if the connector is arranged vertically. The nut plate 5 is released from the threads of the screw 2. In the hypothesis of a vertical arrangement of the connector, it should be noted that gravity would be sufficient, even in the absence of any return member 21, to maintain in contact the shoe 7 and the plate 5 in abutment on the opening 6 of the smooth stud 9. The presence of the return spring 21 makes it possible in fact not to have to take account of the orientation of the connector; its essential role is to be able to oppose the weights of the shoe 7 and the nut-plate 5.

Taking into account the difference existing between the sizes d and e there is a clearance a for the nut-plate 5 between the shoe 7 and the first threads of the screw 2.

 Figure 3 shows the connector in an arrangement where the two shoes 7 and 8 are in contact with the cable 17 to be tightened. The screw 2 is lowered sufficiently towards the cable 17 so that the shoe 7 is no longer in abutment against the opening 6 of the stud 9, but not enough so that the nut-plate 5 is engaged on its threads. The above game, allocated to the nut-plate 5, is therefore partially consumed. There is in fact for the screw 2 a dead travel d reduced by the height of the chamfer 22, during which the pressure shoe 7 is in contact without tightening with the target 17.

 After total consumption of this play a, the start of engagement of the nut-plate 5 on the threads of the screw 2 fixes the axial offset which it presents with the small branch lb: it becomes in practice completely immobilized with respect to the nut part l; already locked in rotation it is now axially blocked because, passing through, in the example under consideration, the nut 1 and the plate 5 according to identical screw threads, the screw 2 moves by turning at equal distances from the members 1 and 5. I1 then exists a predetermined axial offset b between the nut plate 5 and the fixed flange 4. As the threads of the screw 2 penetrate further into the nut plate 5, the flange 4 approaches the latter while a progressive clamping is supported by the cable 17, into which the teeth 13 and 14 are gradually sinking.

 When tightening the configuration of the electrical connector is as shown in FIG. 4: the flange 4 is in abutment against the plate 5 since said plate is practically fixed relative to the part 17 from its engagement on the threads of the screw 2 Consequently, whatever the torque applied to the screw 2 henceforth, there is no additional pressure of the screw on the clamping shoe 7, nor a deeper penetration of the teeth or blades 13 and 14 of the shoes 7 and 8 in cable 17.

 I1 it should be noted that the application on screw 2 of a high tightening torque after abutment of the flange 4 on the nut plate 5 causes the screw to lock in its nut, whence it results in a certain insensitivity to loosening of screw 2 in the presence of vibrations. It can also be observed, with regard to the dimensions of the clamping device, that the initial axial offset b between the elements 4 and 5 represents the sum of the thickness e of the insert less the height of the chamfer 22, the crushing of the cable 17 by deformation, and the cumulative depths of perforation by the teeth 13 and 14.

 At the end of use, the screw is loosened. Firstly, the clamping shoe 7 ceases to be in contact with the active end of the screw 2, while the collar 4 ceases to contact the nut plate 5.

The teeth 13 of the shoe 7 do not start to come out of the cable 17 until the moment when the screw 2 rises, the opening 6 of the smooth stud 9 comes into contact with the shoe 7.

 The loosening operation continues until a complete loosening configuration as shown in Figure 5. The fixed flange 4 is here in abutment against the part lb of the nut. As in the case of FIG. 4, the entire system is blocked and no additional loosening can be obtained. On the other hand, the nut-plate 5 is again free relative to the screw 2, having escaped from its threads; it is applied against the shoe 7 under the effect of the return member 21; the axial play a is restored.

 The presence of the fixed collar 4 constitutes an important contribution of the invention. In fact, in the connectors known to date, it is the shoe 7 which, in the loosening configuration, comes directly into abutment on the nut part, it follows that, if the loosening torque is not moderated, we exerts a considerable tearing force on the rotary crimping formed by the opening 6 of the smooth stud 9 of the screw 2 on the shoe 7. This results in a separation of the screw 2 and the shoe 7 which makes it impossible to reuse the connector . The device according to the invention, on the other hand, prohibits any effort to tear off the shoe 7 by uncontrolled unscrewing of the screw 2, which constitutes a huge improvement in terms of the longevity of the very well known system of fastening by rotary crimping between pressure screws. and pressure shoe.

 In practice, this fixed flange can be an integral part of the screw 2; it can also be formed of a nut or threaded ring immobilized completely in one place of the screw, for example by stamping of the facing threads.

 It should be noted that this immobilization can, if necessary, be only temporary, the axial position of the flange being adjustable, for example, by penetration into the screw of a small screw linked to the threaded flange 4 adapted to penetrate radially into one of a plurality of radial channels formed in the screw. It may also be sufficient in certain cases for the collar 4 to come into abutment only when tightening: it can then be placed on the screw outside the body 1; it can also be obtained by a sudden reduction in the diameter of the screw, according to a transverse plane adapted to come into abutment on the nutplate.

 As for the return member 21, spring, elastomeric tube or other, its role is to restore, as soon as possible during the loosening, the axial play has between screw 2 and the nut-plate 5, and to maintain it whatever the handling conditions of the connector before its next tightening.

 It is important in this regard to note that it is advisable to avoid any untimely engagement of the nut plate 5 on the threads of the screw 2, under the effect of the gravity or the inertia of the parts 5 and 7 by example. Indeed, if this were to happen before the shoe 7 comes into contact with a new part to be clamped, the clamping stroke, from the contact of shoe 7 with said part until the collar 4 comes into abutment on the nut plate 5, it would be reduced: the connector would be completely out of adjustment.

 A positive, rigorous control of the tightening stroke of a connector according to the invention is therefore only ensured on condition that the engagement of the nut plate 5 on the screw 2 does not occur by screwing in 2 in the body 1 only if, and only if, a generally arbitrary body, and for example an insulated cable 17 immobilizes 7 and 5 in their descent in the first phase of tightening. The dimensioning of the parts must be established accordingly.

 In order to fully understand the judicious operation of the device according to the invention, it should be noted that the dimension b previously mentioned is a construction characteristic of an apparatus designed for the use over a determined dimensional range of objects to be clamped, also having defined deformation or crushing characteristics, or penetration by perforation.

It is therefore essential at each reuse of the device to be certain that the dimension b is fully found after the previous loosening; it is therefore absolutely necessary to avoid reusing the device before the nut plate 5 has fallen back on the shoe 7, that is to say that all or part of the game has initial, absolute prerequisite for any suitable and controlled tightening, is reconstituted, even if the release of the body clamped under the shoe 7 could have been carried out before. To ensure that this prerequisite is respected in a simple manner, it suffices to unscrew it completely from 2 to the stop position of the flange 4 on the body 1, this unscrewing thoroughly, without any particular precaution being , as has already been said, without risk for the joining of 2 of 7.

 It is easy to understand that the device according to the invention, described by way of example in the case of an insulation piercing connector is only a special case and that it can be applied to any other use in which we try to simply tighten a more or less deformable body by means of a pressure screw, whose tightening stroke is automatically and positively controlled idea, regardless of the tightening tool used as rudimentary as it is and the torque of the user. Many variant embodiments can in fact be proposed without departing from the scope of the invention.

 We particularly appreciate the simplicity of the system according to the invention as well as its ease of execution in large industrial series and it will be noted that the said system works in an identical manner, with the same effects, for a wide range of dimensional dimensions (diameters for example) of objects to be tightened.

 As regards more particularly the application of the invention to connectors with insulation perforation, the results obtained are reliable and satisfactory due to the low thickness tolerances of the insulators on the insulated cables, in particular those of overhead networks and slight differences in cable crush in a reasonable range of sections. These differences lead, according to the design of the system of the invention, to differences in penetration or deformation under tightening, remaining perfectly acceptable in practice while leaving the user great freedom of maneuver since bumpers both for tightening and 'untimely loosening are automatically given by the system according to the invention.

 In addition, unlike breakable screw systems, the system according to the invention is very easily and infinitely reusable even on bodies, or cables, of successively different dimensions between them, which is a considerable advantage in the case of branch connectors. where it is required that the branch connector 20 be removable and reassemblable several times at the main cable and / or at the branch cable. It is understood that there can be several branch cables on the same connector.

Claims (8)

 1. Clamping device for a part, of the clamp type with controlled stroke for clamping the part (17) between a support shoe (8) secured to a nut part (1) and a clamping shoe (7 ), arranged at the end of a screw (2), in particular for an electrical connector with insulation perforation, characterized by the mounting with clearance of the clamping shoe (7) and of a nut plate (5) immobilized in rotation by does it relate to the nut part (1) on an axial extension (9) of the screw (2), and by the association with the screw of a flange (4) immobilized thereon, at a distance predetermined of said end of the screw (2) o  2. Device according to claim 1, characterized in that the nut part (1) is a U-shaped part of which one branch (16) is crossed by the screw (2), the other branch (lc) carries the shoe d 'support (8) and the middle part (la) has an axial portion (12) adapted to block in rotation the nut plate (5).  3. Device according to claim 1 or 2, characterized in that a chamfer (22) is formed at the end of the screw (2) in order to facilitate its engagement in the nut plate.  4. Device according to any one of claims l to 3, characterized in that a return member (21), such as a spiral spring, working in compression, is interposed, around the screw (2), between the nut part (1) and the nut plate (5).  5. Device according to any one of claims 1 to 4, characterized in that the nut plate (5) is rectangular.  6. Device according to any one of claims 1 to 5, characterized in that the collar (4) is annular.  7. Device according to any one of claims 1 to 6, characterized in that the axial position of the flange (4) is adjustable along the screw.  8. Electrical bypass connector on cable, in particular insulated cable, characterized in that it comprises at least one device according to any one of the preceding claims, the clamped part being the cable (17) or any derivative cable (20 ).