FR2547603A1 - DEVICE AND METHOD FOR CONNECTING THE EDGES OF TWO BANDS - Google Patents

Abstract

THE INVENTION RELATES TO A DEVICE FOR CONNECTING BANDS OF SOFT MATERIAL THROUGH THEIR ENDS. IT INCLUDES A FIRST LAYER 72 OF ADHESIVE CONNECTING THE EDGE 74 OF A HEAT RESISTANT TAPE 68 TO THE EDGE 80 OF A HEAT SENSITIVE TAPE 20, A LENGTH 66 OF HEAT RESISTANT MATERIAL AND A SECOND LAYER 86 D ADHESIVE CONNECTING THIS LENGTH OF MATERIAL TO THE SECOND SIDE OF THE EDGE OF THE TAPE 20. FIELD OF APPLICATION: TREATMENT OF OXIDIZATION OF CABLES IN HEAT-SENSITIVE MATERIAL, FOR EXAMPLE POLYACRYLONITRILE, ETC.

Description

The invention relates to a method and apparatus for joining together

  opposed elongated strips of flexible material, and more particularly a method and apparatus for tuning or splicing a strip of thermosensitive material to a second strip, in a manner designed to protect the end of the heat-sensitive strip when

  subsequent treatment in a high temperature medium.

  It is known to carbonize polyacrylonitrile or other carbonizable material by first oxidizing the material and then heating it in an inert atmosphere to a

  sufficient temperature to carbonize it substantially.

  In the case of polyacrylonitrile, this material is often

  treated in the form of elongated wired strips which are arranged substantially side by side, and parallel to each other, along the band they form.

  This strip is advanced under tension following relatively complex paths defined by rollers within one or more oxidation furnaces before being introduced into a charring furnace. tape makes several passes through different stages of the kiln maintained at temperatures designed to give polyacrylonitrile cords

the desired oxidation.

  The nature of the polyacrylonitrile cords is such that the strip can not be left idle, but

  It must be moved continuously through the oxidation furnace even when the latter is at oxidation temperatures.

  If the tape could remain stationary for any period of time, it would result in rapid and, if necessary, exothermic deterioration of the polyacrylonitrile cords. Moreover, even when the tape is kept moving continuously through the oven, it is not necessary to can tolerate loose ends or knots on the wirings In the presence of free ends or knots, an exothermic reaction usually occurs in the hot furnace resulting in an interruption of the process

  and often the need to stop the entire process and re-introduce the strip into the oxidation furnace while the latter is cold.

  This is the reason why the polyacrylonitrile cable band is generally introduced into the oxidation furnace while the latter is cold. The introduction is carried out by connecting the individual cables at various points along the length of a bar. '

  opposite ends of which the cables are connected.

  These cables are used to pull the threading bar and the connected cords into and out of the oxidation furnace. Since the furnace is cold, the knots and the loose ends of the cords

  o they are attached to the threading bar, do not show any exothermic reaction.

  When the cords were pulled completely through the oxidation furnace by the threading bar, the furnace is turned on and heated to oxidation temperatures during the wire stripe continuing to be advanced. Through the oven It normally takes about two hours in the oven to reach the oxidation temperatures, during which time the strip is drawn continuously through the oven. When the oven has reached the oxidation temperatures, new sections of the strip The preceding sections of the strip, which generally comprise about 90 to 120 kg of polyacrylonitrile cords, must be rejected as waste since the cords in the furnace and pulled through the furnace are oxidized in the desired manner. polyacrylonitrile are relatively expensive, this represents a significant economic disadvantage as far as the cost is concerned.

of the whole treatment.

  It is rarely practical or for any reason possible to maintain such treatments indefinitely in operation because of the need to maintain staff constantly present, 24 hours a day. In addition, 25476 b 3 -3 power outages and other interruptions usually result in the need to allow the oxidation furnace to cool, after which the start-up process described above must be repeated. In addition, the gross cable lengths carried by the feed coils are

  limited, necessitating periodic stops.

  As a result, the loss of large amounts of polyacrylonitrile cords has become a common and necessary feature of these methods. Because of the need for a suitably stretched material web present in the oxidation furnace in preparation for the oxidation of fresh polyacrylonitrile cords, a technique commonly used to stop the process is to scroll through 15 the tape continuously through the oven, even after it has stopped and until it has cooled sufficiently so that the tape can be stopped. At the next start-up, the tape is put back into movement through the furnace and the furnace is heated up to oxidation temperatures The sections of the strip which pass through the furnace during the cooling of the latter, then during its restart, must

  be discarded as waste.

  In some cases, the individual cords of the strip are cut off at the inlet of the oven after the oven has cooled down and the passage of the strip through it has stopped. At this time, the process may It can be started by fixing the strip to be oxidized to the polyacrylonitrile cords remaining inside the oven In such cases, the individual cords of the strip to be introduced into the oven are attached to the individual cords of the strip In the oven interior, after which the advance of the belt through the furnace recommences To prevent the development of an exothermic reaction of the knots and free ends, where the cords are attached to each other, the furnace is placed In stages, each stage is started after the nodes of the cords are fooled. As before, large quantities of polyacrylonitrile cords are lost before the furnace can be brought. the working temperature to start the oxidation of the strip of

desired way.

  When the strip comprises a polyacrylonitrile fabric rather than individual polyacrylonitrile cords, lengths of fabric are joined to each other by various techniques such as those described, for example, in US Patent No. 4,077,822. polyacrylonitrile cordstrips are connected to each other with several layers of a silicone rubber adhesive One of these layers of adhesive is disposed between overlapping strip portions, other layers of adhesive being applied on the outer faces of the overlapping strip portions of heat and pressure are applied for

  maturing the silicone rubber adhesive layers.

  US Patent Application 483,922, filed April 11, 1983 under the title "METHOD AND APPARATUS FOR INTRODUCIJG PEM-SENSITIVE ISTERAL DIO AH Gold ENVIMET", discloses a method in which the polyacrylonitrile tread tape is introduced into the furnace. initial oxidation of a primer in the form of a strip of silica fabric or other heat-resistant material, through the furnace, and then by heating the furnace if the furnace is not already hot The trailing edge of the primer, which remains outside the furnace, is then connected to the leading edge of the carbonizable strand, and the primer is used to pull the strand of cord inside and out. through the hot oven Using the primer

  heat resistant minimizes significantly the loss of carbonizable cords from the web.

  The above application discloses a method for connecting the trailing edge of the primer to the leading edge of the polyacrylonitrile cord strip by taping, stitching and folding the two edges to form loops.

  in which elongated rods are inserted.

  The two edges are then fixed inside a splice bar whose opposite halves have grooves for receiving the two edges and the rods that they enclose. The splice bar can be

  removed to disengage the leading edge of the carbonizable cord strip from the primer after the leading edge 10 has passed through the oxidation furnace.

  Although the technique of connecting the trailing edge of the primer to the leading edge of the polyacrylonitrile cable strand described in the above application has been found to be very satisfactory, it is desirable to have another method and another apparatus for connecting the strips, generally applicable to cases where elongated strips are to be flexibly connected to each other, and to the particular case in which one of the strips is made of a thermosensitive material and must therefore be protected, in high temperature environments, from any development of an exothermic reaction and other problems. The above-mentioned patent No. 4,077,822 gives no indication in this field because it addresses the different problem posed by the connection of different bands of carbonizable cords, without taking into consideration the protection of one of these bands when the other b ande is made of a fabric of silica or other material

heat resistant.

  The invention therefore relates to a method and an apparatus for connecting together elongated and opposite strips, in a flexible manner. The invention also relates to a method and an apparatus for making a connection or a flexible splice, protected against The heat, between an elongated heat-sensitive strip and

another band.

  The method and apparatus according to the invention are intended to provide a flexible connection or splice between opposite elongated strips. When one of the strips consists of a thermosensitive material, this strip is connected to a In a manner that protects the thermosensitive web in high-temperature media When the heat-sensitive web is made of carbonizable material cords, the flexible splice covers the exposed ends of the cords at the edge of the web. to significantly reduce the risk

  development of an exothermic reaction of the cords.

  The joining of a thermosensitive web to a heat-resistant web in accordance with the invention is effected by the application of an adhesive coating on a part of the surface of the web-resistant web.

  heat to form a first layer of adhesive.

  The end of the heat-sensitive tape is then placed on a portion but not on the entire first adhesive layer. A heat-resistant material coating is then used and its underside is coated with adhesive to form a second layer of adhesive. Adhesive layer The coating is then placed over the end of the thermosensitive strip so that the second layer of adhesive, located on its underside, is bonded to the face of the thermosensitive strip opposite the heat-resistant strip as well as that part of the first layer of adhesive protruding from the end of the heat-sensitive strip Heat and pressure

  are then preferably applied to cause the layers of adhesive to cure.

  The heat-resistant coating is preferably substantially dimensionally equal to the first layer or adhesive coating and is applied to generally extend the full extent of the first layer of adhesive. In addition, the strip of heat-sensitive material advantageously covers about 60% of the first layer of adhesive, leaving about 40% of this first layer of adhesive exposed to the second layer of adhesive on the underside of the adhesive layer. coating The ends of the cords defining the edge of the strip

  The heat-sensitive materials are preferably covered with a tape before the heat-sensitive tape is bonded to the first adhesive layer.

  The strip of heat-sensitive material may consist of cords of carbonizable material, for example polyacrylonitrile. The heat-resistant strip and the coating may consist of a fabric of silica or of any other heat-resistant material. adhesive are preferably made of an adhesive at

silicone rubber.

  The invention will be described in more detail with reference to the accompanying drawings by way of non-limiting examples and in which: FIG. 1 is a plan view of an apparatus implementing a method of oxidizing a strip of carbonizable cables; Figure 2 is a perspective view of portions of a contention wire insertion device and an adjacent tension cage forming part of the apparatus of Figure 1; Fig. 3 is a flow chart showing the successive steps of a method for introducing a strip of carbonizable cords into the oxidation furnace of the apparatus shown in Fig. 1; FIG. 4 is a flowchart of the successive steps of a method for making a flexible connection according to the invention and which can be incorporated in the method of FIG. 3; Figure 5 is a perspective view of opposite strips and a coating suitable for illustrating the process shown in Figure 4; and FIG. 6 is an end view of the edges of the opposing strips and the coating of FIG. 5 assembled with intermediate layers.

  of adhesive of the completed flexible coupling.

  The invention can be better understood by first considering a method and apparatus for oxidizing a web

  polyacrylonitrile or other carbonizable cords.

  Since this method and apparatus are described in

  detail in the aforementioned application, it will be referred to only briefly.

  FIG. 1 shows an apparatus used in a continuous process for oxidizing a band of carbonizable cords. This apparatus comprises a frame 10 carrying several creels 12 on which cords of carbonizable material are wound. In the example described, the cords are made of polyacrylonitrile. each cable comprising 3,000 to 12,000 filaments depending, in part,

  the approximation of the cords in the band they form.

  As shown in FIG. 1, the individual cords 14 are unwound from the various creels 12 and are drawn into a device for inserting a compression yarn 16 through a set of combs 18. These combs have the function of guides when the cords 14 are unwound from the creels 12 and pulled to form a relatively flat strip, substantially horizontal 20 at the entrance of the device 16 for insertion of compression yarn The strip 20 has a width of up to 135 cm and can understand

up to 600 cabled 14.

  The device 16 for inserting the contention thread 30 has the function of interweaving a compression thread with the various cords 14 in order to keep them assembled in the band 20 for further processing. An example of a thread insertion device The compression yarn inserted by the device 16 is generally removed after the oxidation and the further processing of the strip 20 so that the cords 14 can be wound up individually or in the form of the apparatus described in US Patent No. 4,173,990. in groups rather than only as part of the entire band 20 After the insertion of the contention wire, the band 20 is advanced in a tension cage 22 comprising a plurality of spaced rollers 24 Inside the tensioning cage 22, the strip 20 follows a sinuous path passing around the various rollers 24 before exiting the cage 22 and

  to be introduced into a first furnace 26 of oxidation.

  The cage 22 of tension is of conventional design and it ensures the band 20 a suitable voltage at its entrance

in the oven 26 of oxidation.

  The oxidation furnace 26 constitutes, with a second

  oxidation furnace 28, an assembly 30 with oxidation furnaces.

  Inside the first furnace 26, the strip 20 follows a relatively sinuous path passing around various rollers

  different 32 mounted at the opposite ends of the furnace 26.

  The strip 20 is taken from the first oven 26 in the second oxidation furnace 28 where it again follows a path

  relatively sinuous passing around several rollers 34 disposed at opposite ends of the furnace 28.

  Although not shown in FIG. 1, the oxidation furnaces 26 and 28 are generally internally divided into several different stages each of which can be maintained at a temperature somewhat different from the temperatures of the other stages. within the furnaces 26 and 28 cooperate with the tensioning cage 22 and with a tensioning cage, located outside the outlet end of the furnace 28, so as to hold the strip 20 under tension. desired while being drawn through the furnaces 26 and 28 At least a portion of the tension results from the removal of the polyacrylonitrile

  constituting the strip 20 when this material is oxidized.

  At the outlet of the second oxidation furnace 28, the strip 20 is directed through the tensioning cage 35 and arrives on a spinning reel 36 where it is stored in preparation for carbonization and other treatment. 35 of tension is of a similar realization

to that of the cage 22 of tension.

  FIG. 2 shows in greater detail a part of the installation of FIG. 1, in particular comprising the device 16 for inserting the contention wire and the tensioning cage 22. As shown in FIG. 2, the individual cords 14 ci are drawn creels 12 through the combs 18 pass between two opposite rollers 38 and 40 where the web 20 is formed. As described in the aforementioned Patent No. 4 173 990, the cords 14 passing between the rollers 38 and 40 are separated from each other. others at one wireline out of two, by links 42 and 44 forming part of the wire insertion device 16 A rapier assembly 46 inserts a compression wire 48 between the separated wires 14 immediately before the latter converge back into a single plan for

  reform the complete strip 20 with the compression yarn 48.

  As shown in FIG. 2, the compression yarn 48

  alternates across the width of the strip 20 forming zig-zag.

  FIG. 3 shows the successive steps of a method for introducing the strip 20 into the oxidation furnaces 26 and 28, this process being described in more detail in the aforementioned application. Initially, a primer, in the form of a elongated strip of heat-resistant material, is introduced into the ovens

  of oxidation 26 and 28, after which the trailing edge of the primer is connected to a leading edge of the strip of cords to be oxidized.

  The primer is then used to pull the strip of cords 30 through the ovens 26 and 28 in which the cords of the strips are oxidized in a desired manner when the leading edge of the cordstrip has cleared from the cages. adjacent to the outlet end of the second furnace 28, this end can be separated from the trailing edge of the primer. The use of a heat-resistant primer allows the furnaces 26 and 28 to be heated to the same temperature. oxidation temperatures before the carbonizable cord strip begins to be introduced into and through the furnaces, minimizing or eliminating the loss of carbonizable cords. As indicated by a first step 52 in FIG. 3, the heat-resistant primer, in the form of an elongated strip of heat-resistant material, for example a silica or aramid fabric, is introduced into the oxidation furnaces 26 and 28 until it has completely or almost completely traversed the furnaces and its rear end remains outside and in the immediate vicinity of the inlet 50 of the furnace 26, the

  Furnaces Which May Be Hot or Cold In a second step 53, the oxidation furnaces 26 and 28 are brought to the oxidation temperatures if they have not already been heated.

  In a third step 54, the leading edge of the strip 20 formed by the cords 14 and produced by the compression thread insertion device 16 is connected to the rear edge of the primer. In a fourth step 56, the advance of the primer through the furnaces 26 and 28 is continued so that the strip 20 is introduced into the oxidation furnaces 26 and 28 and then passes therethrough When the leading edge of the carbonizable cord strip 14 has passed through all the two furnaces 26 and 28 and the tension cage 35, this front edge can be separated from the rear edge

  primer during a fifth step 58.

  In accordance with the method illustrated in FIG. 3, the heat-resistant primer can be introduced into the furnaces 26 and 28 while the latter have already been heated to oxidation temperatures. The primer can remain immobile within the furnaces. In a more typical case where the apparatus shown in FIG. 1 has to be stopped for a certain period of time, the heat-resistant primer is introduced into the furnaces 26 and 28 at the moment when process is stopped and o the furnaces cool down when the

2547603,

  process is then restarted, furnaces 26 and 28 are brought to oxidation temperatures while the primer

  heat resistant stays immobile.

  Meanwhile, the trailing edge of the primer can be connected to the leading edge of the strip 20 so that, when the oxidation temperatures are reached, the primer then the

  strip 20 can be advanced through the furnaces 26 and 28.

  The above-mentioned application N 483 922 discloses a method and apparatus for connecting the carbon towable strip to the heat-resistant primer 78, method and apparatus in which the opposite edges of the strips are covered with opposite lengths of tape, The edges thus formed are then sewn along its length, and then folded back on itself to form a loop into which an elongated rod is inserted. The opposing edges and the rods therein are then disposed between opposite halves of an elongated splice bar, the opposed halves being then pulled together by clamping screws along the bar. so that the opposite strips are fixed inside the splice bar When the latter has passed through the entire oxidation furnaces 26 and 28, the strip 20 can be separated from the temperature resistant primer by loosening the screws along the splice bar so that the opposite halves of the bar are separated and the edges of the strips, previously fixed in the closed off,

be released.

  The invention provides another method and apparatus for making a flexible splice or splice between the strip and the temperature resistant primer, which method and apparatus can also be applied to other media in which the ends The successive steps of this method will be described with reference to FIG. 4, as well as from the perspective view of FIG. 5 and the end view of FIG.

figure 6.

  With reference to FIG. 4, during a first step 64, a coating 66 of glass fabric, aramid or any other heat-resistant flexible material is prepared. As shown in FIG. a width W equal to that of an elongated strip 68 which forms the temperature-resistant primer The strip 68 is also made of a fabric of glass or aramid 10 or any other temperature-resistant material The width W The liner 66 and the strip 68 are approximately 12.5 mm greater than the width of the carbonizable cord 20. The length L of the liner 66 may be

  any suitable value, but it is 25 cm in the example described.

  In a second step 70 shown in Figure 4, a coating or layer 72 of adhesive is applied to the end of the strip 68 adjacent to an edge

  74 of this strip The layer 72 of adhesive is of dimension approximately equal to that of the coating 66.

  In a third step 76 shown in FIG. 4, an end 78 of the carbonizable cord strip 20 is placed on a portion of the adhesive layer 72 so that the strip 68 and the embedded adhesive layer 25 protrude through the Opposite edges of the web 20 by about 6.5 mm Prior to this operation, opposite lengths of tape are applied to opposite sides of the end 78 of the web 20, the sections of the cords protruding from the tape being cut to form An edge 80 on the web 30 FIG. 5 shows a length of tape 82 placed at the top, the opposite and lower ribbon length not being visible in this view. The end 78 of the web 20 is placed on the web. adhesive layer 72 so that it covers it in part, but not entirely. In the example described, the end 78 of the strip 20 covers about 60% of the surface of the adhesive layer 72 so that the edge 80 is about 15 cm from the edge 74 of the strip 68. 10 cm wide

  on which the adhesive layer 72 is exposed.

  In the next step 84 illustrated in FIG. 4, a second layer or thickness of adhesive 86

  is applied to the underside of the coating 66.

  The layer 86 and the first layer of adhesive 72 can

  consist of a silicone rubber adhesive of the type "GE RTV N 31" is a commercial example.

  The coatings or layers 72 and 86 each have a thickness of about 3.2 mm in the example described, but they can have any appropriate thicknesses according to what is required

by the circumstances.

  In a subsequent step 88 indicated in FIG. 4, the coating 66 is placed on the end 78 of the strip 20 and on the exposed portions of the adhesive layer 72 so that this coating 66 and the layer The adhesive layer 86 is applied both to about the same extent as the first adhesive layer 72. The adhesive layer 86 located on the underside of the coating 66 thus binds to the end 78 of the strip 22. and the exposed portions of the adhesive layer 72 The coating 66 having a width W 13 mm greater than the width of the strip 20, protrudes from each of the edges

opposite of this band on 6.5 mm.

  In a next step 90 shown in FIG. 4, heat and pressure are applied to the strips 20 and 68 and to the coating 66, as well as to the incorporated adhesive layers 72 and 86 so as to bring the adhesive It has been found that with the use of stannous octoate as an accelerator, the silicone rubber adhesive matures substantially completely in 5 to 15 minutes under the application of a pressure of 49-105 kPa and at a temperature between 90 and 150 ° C. The heating under pressure can be carried out inside an air press having opposite "Teflon" release leaves placed on hot plates

  opposite inside the press.

  The splice or completed connection is shown in FIG. 6. It can be seen that the end 78 of the strip is included and protected between the heat-resistant strip 68 and the heat-resistant coating 66. The ends of the individual cords constituting The strip 20 is completely surrounded and enclosed at the edge 80 by the coating 66, the strip 68 and the intermediate layers 72 and 86 of adhesive, which minimizes or eliminates the risk of developing exothermic reactions in the high temperature media encountered. In the same time, it turns out that the connection is very strong in addition to being very flexible. At the end of the oxidation or other treatment, the strip 20 can be separated from the strip 68 being cut along the width of the strip 68, in the immediate vicinity of the coupling, or, alternatively, by cutting the coupling itself consisting of the strip 68, the coating 66 , layers of adhesive 72

  and 86 and, where appropriate, a portion of the end 78 of the web 20.

  It goes without saying that many modifications can be made to the described method and apparatus

  represented without departing from the scope of the invention.

Claims (9)

CLAIMS N E N T I N O I T I N N 5   A device for connecting the edge (80) of a first strip (20) to the edge (74) of a second strip (68), characterized in that it comprises a first layer (72) of adhesive connecting the edge of the second strip at the edge of the first strip on a first face thereof, a length (66) of material, and a second layer (86) of adhesive connecting the length of material to the edge of the   first band, on a second face thereof opposite the first face.   2 Device according to claim 1, characterized in that a part of the length of material covers the second band to which it is fixed by a layer of adhesive (86).   3 Device according to claim 1, characterized in that the first strip is heat-sensitive material and in that the second strip and the length of   material are heat resistant material.   Device according to claim 1, characterized in that the first and second layers of adhesive are   consisting of a silicone rubber adhesive.   Device according to claim 1, characterized in that the first band comprises a plurality of cords (14) of carbonizable material, the second band and the length of material are made of silica fabric and the first and second   Adhesive layers consist of a silicone rubber adhesive.   Apparatus according to claim 1, characterized in that the first band is an elongated heat sensitive band, the second band is an elongated heat resistant band having an edge (74) which extends over a first side of the band. the heat-sensitive strip at the edge (80) of the latter, the first adhesive layer comprising a first layer (72) of a flexible material 35 bonding the heat-resistant strip to the first face of the sensitive strip in heat, the length of material comprising a length (66) of flexible, heat-resistant material covering a second opposite face of the heat-sensitive strip, and the second adhesive layer comprising a second layer (86) of flexible material binding the length of flexible, heat-resistant material to the second face of the heat-sensitive strip. Device according to claim 6, characterized   in that the first and second layers of flexible material consist of a silicone rubber adhesive.   8. Device according to claim 7, characterized in that the heat-sensitive strip consists of cords (14) of a polyacrylonitrile composition and that the heat-resistant strip and the length of flexible material resistant to the heat are made up each of a silica fabric.   Method for connecting first and second elongated strips (20, 68) of flexible material, characterized in that it consists in preparing a coating (66) of flexible material, applying a first layer of adhesive (72) on a part of the second band, near an edge (74) thereof, placing one end of the first band, having an edge (80), on the first layer of adhesive, to apply a second layer adhesive (86) on a lower face of the coating, and placing the coating on the first tape so that the second adhesive layer on the underside of the coating bears against the first tape and the coating is placed on the face of the first band opposite to that turned to the second band.   A process according to claim 9, characterized in that the coating is placed on the first strip so that a part of the coating   extends beyond the edge of the first band.   The method of claim 9, further comprising applying heat and pressure to the first and second strips and the coating after the coating is applied to the first strip to bring maturing the first and second layers of adhesive on the second strip   and on the underside of the coating.   The method of claim 9, further comprising wrapping the edge of the first band before the end of the first band is placed, including its edge on the first layer of adhesive.