Abstract:
A method for grounding reinforcement ( 12 ) and composites ( 17 ) on a calender line reduces static build up on the composite ( 17 ), and makes it possible to subject a wire reinforced composite to electron beam processing (EBP). The method employs a slip ring ( 36 ) attached to rolls which contact composite ( 17 ) on the calender ( 11 ), and reinforcement ( 12 ) before it reaches the calender ( 11 ), wherein the slip ring ( 36 ) rotates with the rolls while the rolls are working polymer into the reinforcement, and a terminal ( 34 ) connected to the slip ring ( 36 ) remains stationary, and the terminal ( 34 ) is attached to ground ( 27 ). The method effectively grounds the composite as well as the reinforcement to prevent electrical discharge during EBP.

Description:
TECHNICAL FIELD 
     The invention relates to apparatus and a method of processing elastomeric materials. In particular, the process is directed to a means of producing carbon carbon bonds in a vulcanizable elastomer, and in particular, an elastomer that contains wire reinforcement. 
     BACKGROUND OF THE INVENTION 
     Electron beam processing (EBP) is known in the art for treating elastomeric materials to enhance their green strength. EBP activates carbon atoms in a polymer and induces carbon carbon crosslinking. Carbon carbon cross linking in a green elastomer gives the elastomer added strength that makes it possible in some cases, and easier in other cases, to handle the green elastomer during processing before vulcanization. 
     Electron beam processing is known to induce an electromotive force in wire cords, along with a potentially high voltage, and for such reasons electron beam processing of wire reinforced elastomers has been generally avoided in the past. 
     In prior attempts to provide a means for using EBP on wire reinforced elastomers, a shunt was connected across the wire cords at the beginning of each windup roll. The shunt was then connected to plant ground potential at the windup. 
     On all fabric and wire calender lines, static build-up was removed with wire brushes, which require frequent replacement because of fast wear and lost contact with the sheet product. 
     Previous experiments have shown that the electric potential in a wire-reinforced elastomer that is subjected to EBP can be as high as 2,500 volts, with a very small current (in the milliamp (MA) range). This induced potential can damage an elastomer by arcing from wire to wire in the elastomer, thereby burning the rubber and also causing a safety hazard to the machine operator. 
     It is an object of this invention to provide an apparatus and method, which makes it possible to treat a wire, reinforced elastomer with electron beam processing. 
     It has been found, using the method of this invention, that static build-up that normally occurs when calendering elastomeric products can also be substantially eliminated. 
     Other objects of the invention will be apparent from the following description and claims. 
     SUMMARY OF INVENTION 
     A method of forming a reinforced composite  17  on a calender  11  comprises the steps of a) grounding guide rolls  19  that contact reinforcement  12  from a creel  18  prior to feeding the reinforcement  12  to a calender  11 , b) coating the reinforcement  12  with rubber  23  while on the calender  11  to form a reinforced composite  17 , and c) grounding rolls which contact the reinforced composite as the composite exits the calender  11 . 
     The method in steps (a) and (c) may further comprise the steps of I) attaching slip rings  36  to rolls  14 , 15 , 19 , 21  which contact the reinforcement  12  and the composite  17  on the calender  11 , and II) connecting the slip rings  36  to ground  27 . 
     The method in step (a), comprising grounding reinforcement  12  from a creel  18 , may further comprise the further steps of I) drilling and tapping the end of a roller shaft  32   a  to provide a threaded hole  37  for receipt of a bolt  39 , II) threading a first end of bolt  39  into the threaded hole  37 , III) attaching a slip ring  36  to a second end of the bolt  39 , whereby the slip ring  36  rotates with the roll  32 , IV) connecting a second bolt  38  to bearings within the slip ring  36  and attaching an electrical terminal  34  to the second bolt  38  whereby the terminal  34  remains stationary, and V) connecting the terminal  34  to ground  27 . 
     In one embodiment, the method may comprise the further step of subjecting the reinforced composite to electron beam processing (EBP). 
     In further refinements of the method, the method may include the further step of placing at least one roll above the plane of the reinforced composite and at least one roll below the plane of the reinforced composite. Also, a further step of connecting bare wires to ground during calender changeover may be used. 
     In the illustrated embodiment, the method includes the step of subjecting a calendered sheet comprising rubber-coated wire to an electron beam of 2 to 14 mega-RADs. 
     In the illustrated embodiment, the slip ring  36  is provided as a mercury wetted slip ring. 
     Also provided is an apparatus  10  for grounding materials on a calender  11  which is used to coat wire reinforcement  12  with rubber  23 , wherein the apparatus  10  comprises, a) at least one roll  14 , 15 , 19 , 21  for transporting material through a calender, b) at least one slip ring  36  connected to the roll whereby the slip ring  36  rotates with the roll while a terminal  34  attached to the slip ring stays substantially stationary while the roll rotates, and c) an electrical conductor  26  connecting each of the at least one slip ring  36  to ground  27 . The apparatus  10  may further comprise d) an organizer roll  15  for directing wire through the calender  11 , the roll having a first end of a conductive rod attached at one end thereof, and e) a slip ring  36  attached to a second end of the conductive rod  39 . 
     In an illustrated embodiment, at least one roll is an organizer roll  15 , and the conductive rod is a bolt  39  having a first end threaded into a threaded hole  37  in an end of the organizer roll. Also, a terminal  34  is connected to bolt  38  which is connected to bearings in slip ring  36 . 
     The calender  11  includes apparatus  16  for applying a rubber coat on material passing through the calender  11 . The apparatus  10  may include at least one grounding point on the calendered sheet  17  downstream of the calender  11 , the at least one grounding point optimally comprising a guide roll  21  for the calendered sheet. 
     In the preferred embodiment, the apparatus further comprises an electron beam source  28  associated with the calender  11  down stream of a rubber coating apparatus  16  on the calender  11 . 
    
    
     BRIEF DESCRIPTION OF DRAWINGS 
     FIG. 1 illustrates the apparatus of the invention, which comprises a calender, a rubber application unit, and an electron beam processor. 
     FIG. 2 illustrates the means of grounding potential in the apparatus in one embodiment of the invention. 
     FIG. 3 illustrates a perspective view of organizer rolls, which is part of the embodiment of FIG.  1 . 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     With reference now to FIGS. 1 and 3, the apparatus  10  of the invention comprises a calender  11 , a rubber application means  16 , and an electron beam-processing unit  28 . Those skilled in the art will recognize that when the calender is used for applying rubber to cord reinforcement, a creel  18 , may be used to store cord or filament material that is fed into the calender, and a festoon  20  may be used to collect the calendered sheet of composite material. 
     In the illustrated embodiment of FIG. 1, wires  12  are fed to the calender  11  from a creel  18 , and are directed to the calender via organizer rolls  15 , and coated with rubber  23  at the calender via impression rolls  14 , which are part of rubber application means  16 . As the wires  12  pass through the calender  11 , rubber  23  is applied to the reinforcement  12  by the action of the calender rolls  14  and continues through the calender line until it is collected upon exiting on festoon  20 . The apparatus  10  of the invention includes an electron beam processing unit  28  downstream of the rubber application means  16 , which is used to bombard the newly created, green calender material with an electron beam to induce carbon carbon linkage within the polymers of the calendered sheet  17 . 
     Apparatus and methods for applying rubber to cord reinforcement on a calender, and electron beam processors, are well known to those skilled in the art. 
     The processed calendered material  17  is collected in a roll on a windup (not shown). 
     At least one of impression rolls  14 , and at least one of organizer rolls  15  are connected to ground  27  using electrical conductors  26  (FIG.  2 ). 
     In the illustrated embodiment, there are four such ground connections on the cord reinforcement  12  prior to when the cord reinforcement enters the calender  11 , and there are five such ground connections downstream of the calender, for example on festoon rolls  21 , and optionally cooling drums  45 , which provide static bleed off from the reinforced sheet product. 
     It has been found that impression rolls  14 , festoon rolls  21 , guide rolls  19 , and organizer rolls  15 , and optionally coolin drums  45  are efficient grounding contacts since they cover the full width of the calendered sheet  17 , and the entire surface of the calendered sheet passes over or under the rolls. 
     Although the grounding system developed for the present apparatus was intended to reduce the induced potential created by electron beam processing, it has been found that the grounding system also effectively eliminates static buildup on calendered sheets that do not contain wire reinforcement. 
     With reference now to FIG. 2, in the illustrated embodiment, connection to ground is obtained by attaching a slip ring  36  to the end of each of the roll where a ground connection is made, wherein the bearings in slip ring  36  permit the slip ring  36  to rotate with a roll  32  while isolator  35  permits terminal  34  to remain stationary. 
     The slip ring  36  may be attached to a roll  19 ,  15 ,  14 ,  21  by any convenient mechanical means, for example a rod welded to the end of a roll shaft  32   a.    
     In the embodiment illustrated in FIG. 2, wire  12  passes over roll  32 , which has a drilled and tapped hole  37  in one end thereof. As used herein, roll  32  represents generically any of the rolls associated with the calender which may be connected to ground. 
     In the illustrated embodiment, a bolt  39  is threaded into drilled and tapped hole  37  and held tightly in place by nut  40 . Slip ring  36  is carried on bolt  39 , and rotates as roll  32  rotates. Bolt  38  is connected to bearings (not shown) in slip ring  36 , whereby the rotation of slip ring  36  is isolated from bolt  38 . Therefore, bolt  38  remains stationary while slip ring  36  and roll  32  rotate. In the illustrated embodiment, terminal  34  is held on bolt  38  by nuts  42  and  44 . Terminal  34  is connected to electrical conductors  26 , which are connected to the factory ground  27 . 
     Terminal  34  fits over bolt  38 , and when attached to bolt  38  may make electrical contact with the slip ring assembly directly through bolt  38 , or indirectly through nuts  42  and  44 . 
     In the method of the invention, using the apparatus  10  described herein, a reinforced composite  17  is formed on a calender  11  comprising the steps of a) grounding guide rolls  15 , 19  which are used to feed the reinforcement  12  to a calender  11 , b) coating the reinforcement  12  with rubber  23  while on the calender  11  to form a reinforced composite  17 , and c) grounding rolls  21 ,  45  which contact the reinforced composite  17  after the composite exits the calender  11 . 
     In the illustrated embodiment, the method further comprises attaching slip rings  36  to rolls  14  that contact the reinforcement  12  and the composite  17  on the calender  11 , and connecting the slip ring  36  to ground  27 . 
     In the method, step a) may further comprise grounding reinforcement  12  by 1) drilling and tapping the end of a roller  32  or shaft  32   a  to provide a threaded hole  37  for receipt of a bolt  39 , 2) threading a first end of a bolt  39  into the threaded hole  27 , 3) attaching a slip ring  36  to a second end of the bolt  39 , and 4) connecting the slip ring  36  to ground  27 . 
     In the illustrate embodiment, the method further comprises the step of subjecting the reinforced composite  17  to electron beam processing. 
     In further embodiments of the method, at least one roll is provided above the plane of the reinforced composite, and at least one roll is provided below the plane of the reinforced composite. 
     In the method step wherein electron beam processing is used, the electron beam may comprise a beam of 2 to 14 mega-RADs. 
     In a preferred embodiment, the slip rings  36  are mercury wetted slip rings. 
     As an added safety feature, it is proposed to run a certain amount of bare reinforcement through the calender  11  so that ground can be established with bare wires at both ends of the calender  11  before the rubber application step is begun. In addition, an additional section of uncalendered reinforcement can be run through the calender after rubber application and electron beam processing is completed, to assure that the reinforcement in the calendered sheet  17  is grounded at all times. 
     The invention is further illustrated with reference to the following example. 
     EXAMPLE 
     In this example, the method and apparatus of the invention are used to treat a wire-reinforced product with electron beam processing (EBP). 
     The calender was modified to provide nine ground points throughout the line. Four grounding points were established on roll, which contact the wire reinforcement before the wire reaches the calender. Five additional grounding points were established downstream on the calender, and after the calender, as an added safety factor, and to reduce static buildup on the calendered sheet and to ground the bare cords during calender changeover. 
     Prior to energizing the EBP unit, all connections were carefully checked, and it was verified that when steel cord was in contact with the grounded rollers, they also were at ground potential. 
     While the calender was running, and the electron beam-processing unit was in operation, attempts were made to measure any induced voltages in the wire cord. No voltages were observed on AC and DC settings on the voltmeter. The lack of induced voltages was further confirmed by static meter readings throughout the line, whereby negligible readings were observed. These tests were carried out using normal dosages of electron beams. 
     The test was repeated by doubting the output of the electron beam processor, and the same results were achieved. 
     While the invention has been specifically illustrated and described, those skilled in art will recognize that the invention may be variously modified and practiced without departing form the spirit of the invention. The scope of the invention is limited only by the following claims.