Patent Publication Number: US-10315882-B2

Title: Spool fixation device with bi-stable magnet assemblies

Description:
The invention relates to a spool fixation device for use in a pay-off or take-up unit of wire handling or processing machinery. 
     BACKGROUND ART 
     Wires of long length are carried on spools of all kinds. These spools enable the efficient transport and handling of the wire without the wire getting entangled or the end getting lost. Wire spools are rotating in machinery on rotatable axes supported at both ends, cantilever axes with a counter fixture, on vertical spindles or between two rotatable pintles. As the spools are many times running at high to very high speeds it is a matter of elementary safety that they should be held firmly during rotation. 
     When a spool runs empty (or full) their replacement with full (or empty) spools should go smoothly, safe and with little effort in order not to lose time in the production process. Sometimes spools are well adapted for their use in unwinding but may not be optimal for winding wire on. For example the bore hole of a spool may be small and sufficient for the use on an axis of a pay-off installation running at low speed and low tension. Unfortunately, the same bore hole size may not be adequate to use the same spool on a take-up unit where winding forces and winding speeds are higher. 
     This becomes particularly relevant when the wire is rather heavy such as in the case of metal wires like steel wires, steel filaments or steel cords. The weight of wire held by the spool is high due to the high specific weight of steel and the long lengths involved. The mass of wire held by a spool may vary between 5 kg to 500 kg while the spool itself may weigh between 0.5 to 50 kg. 
     Typically spools are mounted by sliding the bore hole over a cantilevered shaft mounted on a rotatable disc. A cantilever mount is many times preferred as the side opposite to the rotatable disc remains free and accessible to the operator. No counter support is needed provided the spindle has sufficient diameter to hold the load. Only a chuck is needed to secure the spool on the spindle. Usually a drive pin is mounted on the rotatable disc that engages with an off-centre drive hole in the spool. In this way torque is transferred between the driven or braked rotatable disc and the spool. The loading of an empty spool can be pretty challenging for the operator in that he must first aim to insert the shaft into the bore hole and then to engage the drive hole with the drive pin. Any improvement made to the loading or unloading of empty or full spools on a steel wire processing installation is therefore welcomed. 
     Various solutions have been suggested to hold spools on their shafts, in particular for cantilever mounted spools. As the spools used are generally made of steel that can be attracted by a magnet it may therefore seem a plausible solution to use magnetic force to hold the spools to the installation. However, the use of magnetic forces to mount spools seems in general to be disliked:
         When electromagnets are used a constant supply of current is needed towards a turning disc implying a rotative electrical contact. The rotative contact is prone to wear. Upon an electricity failure, the spools are no longer held and can come lose from the spindle. Also electromagnets do consume a lot of energy when active.   Permanent magnets—as described in U.S. Pat. No. 3,396,919—can only be used for spools with low masses as the spools have to be pulled off from the rotatable disc thereby overcoming the magnetic attractive force. For heavy and full spools such force is difficult to overcome manually.       

     The inventors have therefore come up with the following solution. 
     SUMMARY OF THE INVENTION 
     The primary object of the invention is to improve on the existing art of spool fixation in wire winding installations, more specifically steel wire—such as steel filament or steel cord—installations. It is an object of the invention to make spool replacement to go swift, effortless and safe for the operator while not consuming a lot of energy of any kind. It is a further object of the invention to be able to process small bore hole spools in a cantilever mount. It is a still another object to dispense with the need of having a drive pin to transfer torque from the spool fixation device to the spool. 
     According a first aspect of the invention, a spool fixation device is claimed that primarily comprises a rotatable flange for holding a spool. The rotatable flange is rotatably attached to the wire winding installation and can be driven or braked or turn freely. The spool to be used must at least have a flange that is magnetically attractable. Most metal spools made of steel sheet are suitable. The rotatable flange is provided with one or more magnet assemblies. The magnet assemblies are mounted directionally compliant to the rotatable flange. Characteristic about the device is that the one or more magnet assemblies can be set to a ‘hold’ state for magnetically holding the flange of the spool against the rotatable flange or can be set to a ‘release state’ for removing the spool from the flange. 
     The magnet assemblies are by preference radially mounted around the axis of rotation of the rotatable flange. Angularly the magnet assemblies are distributed in agreement with the symmetry of the spool flange contacted by the magnet assemblies. The spool flange may have reinforcement ribs on which the magnet assemblies have little grip. So the magnet assemblies are mounted in positions between those reinforcement ribs where there is a flat surface. 
     Typically four to eight magnet assemblies are mounted on the rotatable flange, although nothing forbids that less (one, two or three for example) or more (up to twelve for example) can be used in order to ensure sufficient holding force. The more magnet assemblies are present the more holding force but also the more costly the whole device becomes. 
     The magnet assemblies are mounted ‘directionally compliant’ to the rotatable flange. Thereby it is meant that the surface of the magnet assembly that comes in contact with the flange of the spool can slightly swivel but not significantly translate (less than 5 mm) perpendicular to the rotatable flange. This allows the magnet assembly to take that orientation that results in the largest possible magnetic holding force. Typically the normal to the spool contacting surface of the magnet assembly can deviate up to 5° from the normal on the rotatable flange. This directional compliancy can be achieved by means of an axial retainer means such as a bolt with spring washers, ball joint, or elastomeric joint. 
     The geometrical area of the magnet assembly that comes into contact with the spool flange may be adapted for maximal surface contact to the flange. If the spool flange is separated in sectors by the radial reinforcement ribs, the contact surface of the magnet assembly may be of substantially triangular shape, fitting into the flange sector. Alternatively the contacting surface may be of circular, square or segment shape. 
     According a first preferred embodiment each magnet assembly comprises a permanent magnet array that is sealed from the outside in a housing. The housing must be substantially non-magnetic at least in the direction facing the spool flange. The backing may or may not be magnetically attractable. The permanent magnet array comprises a number of individual permanent magnets. Nowadays very strong permanent magnets based on rare-earth metal alloys exist. Typical examples are neodymium-iron-boron (Nd 2 Fe 14 B) and cobalt-samarium (Co 5 Sm) compositions. These materials show high remanent magnetisation and high coercitive fields i.e. have a strong magnetic induction and are difficult to demagnetise making them the ideal materials for use. Alternatively older materials such as ‘alnico’ (an alloy of iron, aluminium, nickel and cobalt) can also be used. As the high performance magnets are usually prone to corrosion they must be sealed individually (by coating with nickel, copper or embedding them in a resin) and sealed from the outside in a non-magnetic housing made of for example a non-magnetic metal alloy or a polymer housing. 
     Typically the permanent magnet array will comprise an even number of permanent magnets arranged in a planner pattern with the magnetisation perpendicular to the plane of the magnets. South and North poles of adjacent magnets are opposed so that magnetic field lines fringe out maximally. For the kind of application envisaged and depending on the weight of the full spool, a single permanent magnet array must have a holding force of at least 1 kN, or more than 2 kN or even better than 5 kN. By increasing the number of magnet assemblies in the device the holding force can further be increased. 
     According a second preferred embodiment the magnet assembly only requires an energy input when in the release state. When the device is in the ‘hold’ state—i.e. during rotative operation—no energy input is needed. As the spool will only be released from the spool fixation device when it is standing still, energy input is only then required. Once the spool has been removed from the device, the energy input can be stopped again thereby automatically returning the device to the ‘hold status’. This is a big advantage in terms of energy and safety compared to for example electromagnets wherein energy input is needed while the spool is rotating and not when it is standing idle. 
     According a third preferred embodiment of the invention, the magnet assemblies only require an input of energy when switching state. When the magnet is in the ‘hold’ state or the ‘release’ state, they remain in that state until a short pulse of energy is fed to the assemblies switching them to their alternate state of ‘release’ or ‘hold’. This embodiment uses even less energy than the second embodiment. 
     The setting of the state of the magnet assemblies can be done conjointly or in series. The energy input can be one or two out of the group comprising electrical, pneumatical, hydraulical or mechanical energy as will be explained hereinafter. The energy is fed through an energy coupling that can be a rotatable energy coupling between the stationary wire winding installation and the magnet assemblies on the rotatable disc. However, due to the fact that only energy must be supplied when the rotatable flange is standing still i.e. during unloading or loading of a spool, this coupling needs only be realised at stand still which greatly reduces the cost of the coupling and greatly increases safety of the spool fixation device. This in contrast with for example electromagnetic assemblies where the electrical coupling must remain established during operation. Any loss of current supply during operation (for example due to a failing electrical contact or a power trip) results in a release of the spool which is highly dangerous situation. Preferably, the coupling is coaxial to the axis of rotation of the rotatable flange. The stationary part of the coupling is considered part of the spool fixation device (whether in a coupled state or not). 
     The making or breaking of the coupling may also need an energy input. A preferred embodiment of the energy coupling is an energy coupling which is physically made and broken by the same type of energy that is transferred. The coupling is broken when the spool fixation device is operative and is active when the spool fixation device is stationary. For example the coupling of pneumatic energy is activated or broken between installation and magnet assemblies by means of pneumatic energy. Even more preferred is that the coupling is realised by the very same energy input as the energy input to the magnet assemblies. For example an electrical connection between installation and magnet assembly is made or broken by the current running through the coupling to the magnetic assembly. 
     In a fourth preferred embodiment the permanent magnet arrays are alternatingly moveable in said magnet assemblies from a position close to the spool flange for strong attraction of the spool flange—i.e. when in the ‘hold’ state—to a remote position away from the spool flange for weak attraction of the spool flange—i.e. when in the ‘release’ state. As the magnetic field attraction readily drops of with distance (with the inverse cube of distance) the attraction is short ranged and the close and remote position need not be that far from one another. For example a few centimeter suffices to have the spool released. 
     However, in order to come from a ‘hold’ state to a ‘release’ state the holding power of each individual permanent magnet array must be overcome. Therefore an energy input is needed. Preferably this is done by a pneumatic system wherein a pressurised fluid is used to separate the permanent magnet from the spool flange and to move it sufficiently far away so that the attractive force becomes negligible. Typically a pressure of 2 to 6 bar is needed. When now a mechanical spring is mounted behind the permanent magnet, the permanent magnet will remain in remote position as long as the pressure is on and the spring will move the permanent magnet to the close position when the pressure is removed. Instead of a mechanical spring, a pneumatic spring can be used. So two types of energy input are used: pneumatical and mechanical or pneumatical 
     Alternatives are that an electromagnet is used to move the permanent magnet from the close position to the remote position. A pulse of electrical current (i.e. energy) will have to be supplied in order to pull back the permanent magnet. By putting a ferromagnetic backing plate to the non-magnetic housing, the permanent magnet can be held in remote position without supply of current. By giving a reverse pulse of current to the electromagnet the permanent magnet can be moved into the close position. In this case both inputs of energy are electrical. 
     In a fifth preferred embodiment, the permanent magnet array can be shunted to make the array inactive. By relatively moving a magnetic shunt in between the permanent magnet array and the spool flange the field of the permanent magnet array is diverted into the shunt and the spool flange is released. Alternatively when the magnetic shunt is turned away from before the permanent magnet assembly, the magnetic field of the permanent magnets can extend into the spool flange and attract the spool. A magnetic shunt is a ferromagnetic piece of material of for example iron. 
     In a further improvement of the spool fixation device the magnet assemblies are provided with a high-friction layer at least at the surface area intended to contact the spool flange. As friction is determined by the interaction of on the one side the surface of the spool and at the other side the high-friction layer, both those surfaces can be optimised for optimal friction. For example the surface of the spool contacting the magnet assembly can be made rough or serrated while the high-friction layer is made of a rubber (or just the other way around). Alternatively, when the surface of the spool is very smooth—in case of e.g. a painted spool—the rubber pad on the magnet assembly may be provided with flexible suction cups. A high friction between spool surface and magnet assemblies is desirable as when the spool is driven considerable shear forces occur between the spool flange and the magnet assembly. Hence, not only the spool retention perpendicular to the rotatable flange must be high, but also in shear direction i.e. in the plane of the rotatable flange. Alternatively, when reinforcing ribs are present on the spool flange, these ribs may prevent gliding of the magnet assembly on to the spool flange when torque is applied to the spool. 
     A drive pin on the rotatable flange and a fitting drive hole in the spool are therefore no longer necessary in the spool fixation device according the invention. This greatly facilitates the mounting of the spool as the operator does not longer has to aim to engage the drive pin into the drive hole of the spool. 
     A centering pin remains necessary to keep the spool to be held in the centre of the rotatable plate. An off-centre spool cannot be tolerated. However, the centering pin does not have to extend through the complete bore hole due to the fact that the spool is also carried by the rotatable flange. In addition spools with small bore hole can also be processed on the wire winding installation with this spool fixation device. In prior-art wire winding installations using spools with small bore holes (say 33 mm or less) the shafts are subject to fatigue as all weight and wire forces are transmitted to the shaft. As now a considerable force is taken by the rotatable flange small diameter centering pins can be allowed and do not even have to span the whole width of the spool. 
     However, for even heavier spools a centering pin or shaft extending about the width of the spool can still be used. In that case a counter centre or holding chuck can be provided at the end opposite to the rotatable flange in order to secure the spool additionally. 
     According a second aspect of the invention, a wire winding installation is claimed. The wire winding installation can be a pay-off or take-up installation comprising one or several spool fixation devices according the invention as disclosed above and in the claims. Such a winding installation can take small bore hole spools without a drive hole. 
     According a third aspect of the invention a wire spool that is specifically suitable for use with the spool fixation device is disclosed. The spool has at least one flange that is magnetically attractable. Therefore sufficient magnetisable metal must be present. Steel sheets with thickness between 1 to 4 mm such as 3 mm will generally suffice to be held magnetically. Typically spools with a full load mass between 10 and 800 kilograms are envisaged to be used with the spool fixation device. Specific about the spools is that at least the areas of the flange that are contactable by the magnet assemblies are provided with an anti-slip coating. This to improve the shear force resistance of the spool fixation device. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  shows the spool fixation device in perspective view. 
         FIG. 2  is a cross-sectional view of a first embodiment of a magnet assembly. 
         FIG. 3  is a cross-sectional view of a second embodiment of a magnet assembly. 
         FIGS. 4 a  and 4 b    are cross-sectional views of a third embodiment of an exemplary magnet assembly. 
         FIGS. 5 a  and 5 b    are axial cross sections of an embodiment of the energy coupling. 
         FIG. 6  shows a spool that is specifically designed for use with an embodiment of the spool fixation device. 
     
    
    
     The first digit in the reference in the numbers refers to the figure number. In  FIGS. 2 to 4  equal tens and unit numbers refer to equal or similar items. 
     DETAILED DESCRIPTION OF THE INVENTION 
     A perspective view of the spool fixation device is shown in  FIG. 1 . Basically the device comprises a rotatable flange  102  on which magnet assemblies  104 ,  104 ′,  104 ″,  104 ′″ are mounted. The magnet assemblies slightly protrude above the plane of the rotatable flange  102 . As known in the art the rotatable flange is mounted fixedly to a co-rotating axis  106 . A centering pin  108  is mounted centrally to centre the spool on the spool fixation device. The centering pin  108  protrudes from the rotatable flange  102  with a length ‘L’. An energy coupling  110  is provided at the end of the axis  106 . The spool fixation device is mounted by the axis  106  in a wire winding installation (not shown) such as a winding bench for 12 or 24 or more spools. The full spools in this kind of installation have a mass of more than 100 kilogram. Note that no drive pin to transfer torque to the spool is present on the rotatable flange  102  as in prior art installations. 
     The centering pin  108  does not have to extend through the complete bore hole of the spool. When the width of the spool is larger than the length ‘L’ of the centering pin, the spool is partly carried by the centering pin and partly by the rotatable flange  102  in contrast with prior art installations where the full weight of the spool is carried by the cantilever shafts. Nevertheless the use of a centering pin that extends through the bore hole of the spool i.e. protrudes at the spool flange opposite to the rotatable flange  102  remains possible. In that case the length ‘L’ of the centering pin is larger than the width of the spool. 
       FIG. 2  shows a first embodiment of the magnet assembly  200 . The magnet assembly is held in a round box  218  that is fixedly mounted on the rotatable flange  220  by means of bolt  222 . The non-magnetic housing consists of a cylindrical body  206  of aluminium with a front cover  204  made of brass. The back cover  208  is made of magnetisable ferritic or martensitic stainless steel. The housing seals the internal permanent magnet array  203  from the outside environment. The magnet array  203  comprises six permanent magnets  202 ,  202 ′,  202 ″ (other magnets are not shown) arranged in a hexagon and held in a polymeric holder made of cast resin. The permanent magnet&#39;s field are arranged alternating between adjacent magnets. The permanent magnets are by preference Hicorex®, high performance magnets of the NdFeB type obtainable from Hitachi Magnetics corporation. 
     The permanent magnet array  203  can move from a position close to the front cover  204 , to a position remote from the front cover indicated with a light dashed line  203 ′ in  FIG. 2 . To this end the round permanent magnet array  203  is provided with a pair of circumferential sealing rings  224 ,  224 ′. The seal rings are by preference high elastic and wear resistant Viton® seal rings. By pressurising the air input  216  the magnet array is pneumatically pushed from the position close to the spool to a position  203 ′ more remote from it. In order to allow the pressure to spread between magnet array and front plate  204  the front plate or the magnet array may have cut-in channels. 
     The magnet assembly is mounted directionally compliant in the box  218 . This is achieved by a spring  210  and bolt  212  mount. In this way the magnet assembly can swivel inside the box  218  but cannot be pulled out as the bolt  212  prevents this. 
     Once the magnet array has reached the remote position  203 ′, the air pressure can be released as the magnet array is now slightly attracted by the weakly magnetisable back cover  208 . When all the magnet arrays in the respective magnet assemblies  104 ,  104 ′,  104 ″ and  104 ′″ are in the remote position i.e. the ‘release’ state, the spool can be removed from the spool fixation device as the flange of the spool is released from the rotatable flange  220 ,  102 . 
     When now an empty spool has been slid over the centre pin  108 , the magnet assemblies can be set to the ‘hold’ state by air pressurising line  214 . The magnet array is then moved from the remote position  203 ′ to the close position  203  thereby holding the flange of the spool magnetically. Once the spool flange is attracted by the magnet arrays, the air pressure can be removed and the spool may start turning without any further energy input to the magnet assemblies. This is one of the major advantages of this spool fixation device: there is no need for an energy input to hold the spool during operation. Another advantage of this embodiment is that only an air pulse is needed when changing state. 
     In order to increase the shear force resistance of the spool flange relative to the magnet assembly during winding, the front cover  204  is provided with a vulcanised rubber layer  226 . This rubber layer adheres very well to the brass front cover  204 . By preference it is less than 1 mm thick in order not to weaken the magnetic attraction. 
     Another advantageous embodiment of the magnet assembly  300  is shown in  FIG. 3 . In this embodiment the back cover  308  is made of aluminium. The directional compliance is achieved through a resilient collar  310 —made of rubber —and a ball bolt  312 . Analogously with the previous embodiment, the magnet array  303  is composed of six permanent magnets with alternating polarity. Now line  314  centrally feeds pressurised air through centre tube  316  to between the front cover  304  and permanent magnet array  303 . Sliding seals  324 ,  324 ′ ,  324 ″, and  324 ′″ ensure sealing. When now pressurised air is supplied through line  314  the magnet array will move away from the position close to the spool. A conic spring  315  pushes the magnet array back, but the force of the spring is overcome by the force exerted by the pressurised air. 
     As long as the pressure remains on, the magnet array  303  remains in remote position i.e. the release state. As soon as the pressure disappears, the magnet array moves to the ‘hold’ state under action of the spring  314 . There are therefore two different kinds of energy input: mechanical (the spring) and pneumatical. The advantage of this embodiment is that only one air feed line  314  is needed. On the other hand pneumatic energy is needed as long as the magnet array is in the release state. However, normally this will not take long as the time needed to remove or mount a spool is relatively short. In between removing and mounting a spool the pressure can be released. 
     A further embodiment of a magnet assembly is shown in  FIGS. 4 a    and  FIG. 4 b    that is a cross section through plane AA of  FIG. 4 a   . Again the assembly is mounted directionally compliant in box  418  through ball bolt  412 . But now the four magnets  402 ,  402 ′,  402 ″ and  402 ′″ remain stationary in the assembly. A shunt  430  made of a ferromagnetic material such as iron is mounted between front cover  404  and the permanent magnets. The segmented shunt  430  can turn in front of the poles of the permanent magnets by turning axis  414 . Friction between magnets  402 ,  402 ′,  402 ″,  402 ′″ —as the magnets strongly attract the shunt  430 —is diminished by putting a low friction layer  432 —such as Teflon® film-between magnets and shunt. Switching states is now realised by turning axis  414  (mechanical energy input). When the shunt  430  is turned in front of the magnets, the magnetic field is diverted through the shunt  430  and considerably weakened near the spool flange. Clearing the magnets from the shunt will enable the magnetic field to attract the spool again. 
     A convenient pneumatic energy coupling  110  between the wire winding installation and the spool fixation device is shown in  FIG. 5 a    in the open state (for example during rotation of the axis  106 ) and in  FIG. 5 b    in the closed state (when the axis  106  is stationary). The coupling is specifically convenient to cooperate with the magnet assemblies of the second embodiment ( FIG. 3 ). 
     During the operation of the installation, the magnet assemblies do not need energy and no pneumatic input is needed through feed tube  514 . Then axis  502 —corresponding to axis  106  in  FIG. 1 —is turning while the coupling housing  504  remains stationary attached to the wire winding installation. Housing  504  and axis  502  are centred to one another through ball bearing  506 . 
     The coupling is provided with a piston  516  axially moving on feed tube  514  in housing  504  and sealed by means of seals  518  and  518 ′. The piston pushes against elastomeric expandable seals  510 ,  510 ′ that are held by the centre bored nut  508  that is threated on the feed tube  514 . Elastomeric expandable seal  510  is attached to piston  516 . The inner seals  520 ,  520 ′ must therefore not be of high quality or can even be replaced with circlip rings. 
     When now the axis  106 / 502  has come to standstill and a spool is to be removed or loaded, the pressure chamber  530  is charged with pressurised air through inlet  512  as shown in  FIG. 5 b   . The piston  516  compresses the elastomeric expandable seals  510 ,  510 ′ that thereby radially expand and provide a seal between the hollow axis  502  and the feed tube  514 . Now compressed air can be fed through feed tube  514  that on its turn will put the magnet assemblies  104 ,  104 ′,  104 ″ and  104 ′″ in the ‘release’ state. A split tree is provided in the axis  106  to feed all magnet assemblies at the same time. 
     When the magnet assemblies are to be put in the hold state the pressure on feed tube  514  is released. Thereafter air is released from pressure chamber  530  and the elastomeric expandable seals push back piston  516  into the open position. The pneumatic coupling between rotatable axis  502 / 106  is now removed and the axis can freely turn. In this way the use of a rotatable seal—i.e. a seal between coaxial axes freely rotating relative to one another—can be prevented. Rotatable seals are maintenance intensive and prone to wear. 
     The operation cycle can further be simplified by using appropriate differential valves between inlets  514  and  512  and the pneumatic air supply such that the whole cycle can be completed from one source. 
       FIG. 6  shows a spool that is specifically adapted for use with the spool fixation devices as explained here before. The spool  600  is made of steel sheet of 4 mm thick. As usual ribs  604  are stamped in the metal sheet to reinforce the flange. It is therefore that the magnet assemblies  104 ,  104 ′,  104 ″, and  104 ′″ are protruding out of the plane of the rotatable flange  102  in order not to be hampered by the ribs. It goes without saying that the symmetry of the reinforcement ribs  604  (in this case 8-fold) must be compatible with the symmetry of the magnet assemblies (in this case 4-fold). Between the ribs the flat sectors that may come in contact with the magnet assemblies are provided with an anti-slip coating  610 . If the magnet assemblies are provided with a rubber cover a suitable anti-slip coating may be a rough or serrated coating such as for example obtained by coating with a sand containing paint. When using such spool there is no need to align a drive hole with a drive pin which greatly simplifies the mounting of the spool.