METHOD AND DEVICE FOR IMPARTING ANTI-FRICTION PROPERTIES TO A METALLIC WIRE

Abstract: A method and a device for coating a wire (2) with a lubricant wherein the lubricant is melted in connection with the substance being supplied to a dispensing container (9) and is transferred from the dispensing container to an applicator (4) in the form of a porous body comprising a fibrous material, in which the porosity of the body is completely or partially filled with a lubricant, by the capillary forces in the pores of the applicator and a sub-atmospheric pressure generated when melted lubricant is consumed at the contact surface between the applicator and the wire.

Description: Method and device for imparting anti-friction properties to a metallic wire TECHNICAL FIELD The present invention relates to a method and a device for achieving anti-friction properties in a metallic wire by coating the wire with an anti-fricti ' on substance (lubricant) before a subsequent winding, coiling, bending, curving, or other shaping of the wire. The invention preferably relates to a method and a device in which the lubricant is applied by means of an applicator, which is arranged in the form of a porous fibrous 1 aterial whose porosity is completely or partially filled ,'ith a lubricant for coating the wire. BACKGROUND ART Manufacturers of metallic wire for use as insulated winding wire in electric windings coat the wire with a lubricant in order to impart good anti-friction properties to the wire. By a lubricant is meant in this application a paraffin, a wax, or another substance with a lubricating effect, or a mixture of two or more of these substances. The melting temperature of commonly occurring lubricants is between 50 and 70 °C. Users of insulated winding wire, for example those who manufacture electric machines or components, are very dependent on the wire to have good anti-friction properties along its entire length without interruption. Good anti- friction properties allow the wire to be positioned in an application, and allow the wire to easily slide into position such that the winding does not take up larger space that is required by the application. Also manufacturers of metallic wire for use as resistance wire, for example wire for heating coils, coat the wire with a lubricant, one reason for this being for the wire to easily slide into the desired position, and another reason being to reduce the wear on tools which are used for coiling or other form of shaping wherein the wire is bent or curved. Usually there is used a lubricant which is solid during winding and coiling, respectively, such as a paraffin, a wax, or another substance with a lubricating effect, or a mixture of two or more of these substances. The melting temperature of commonly occurring lubricanes is between 50 and 70°C. When coating a metallic wire with such a lubricant, the substance is dissolved in an organic solvent such as described in US patent specifications US 4 545 323 and US 4 38-5 435, for example petrol, but alto other volatile organic solvents are used. Since normally ve.-y small quantities of lubricant is to be applied to the 'wire, tne concentration of such substance in the solvent is low. The solution normally has a solid content of between 0.05 % and 1 %. The solution is applied to the wire by allowing the wire to pass through a woven tape or cloth, or a felt to which the solution has been added, preferably by the tape/cloth/felt sucking up the solution. Considerable health hazards and safety risks exist in connec¬ tion with the handling of these very inflammable and volatile solutions. In addition, the volatile solution evaporates from the coated wire into the air, which entails a negative load on both the indoor and outdoor environment. The method also entails disadvantages from the quality point of view since it is a problem to control the applied amount of lubricant. Another known method is to impregnate string or other form of twined or woven wire with a lubricant of the same type as mentioned above. By winding the string impregnated with lubri¬ cant a number of turns around the wire, the lubricant will melt by the intrinsic heat of the wire and is applied to the wire. However, in this method the string often breaks. Such a rupture leads to the wire being completely without lubricant over a long distance until efforts have been made by the operators to join the string together. In addition, it is difficult to obtain an even distribution of lubricant around the wire since most of the substance melts from the string on the first 90 degree segment. The equipment is complicated, which entails high investment costs. The cost of string and maintenance is judged to become considerable. The object of the invention is to solve the above-mentioned problems when applying lubricant to a wire, such that the need of using solvent in any .form is eliminated. Another object of the invention is to suggest a method and a device in which the amount, of lubricant applied to the wire can be controlled at any time and at any point of the surface of the wire, and can be changed by simple setting during the application. It is a further object of the invention to suggest a method and a device to apply and distribute lubricant on a wire, irrespective of the diameter of the wire. Yet another object of the invention is to suggest a device with a simple composition with few movable parts to obtain a high reliability at a low cost. SUMMARY OF THE INVENTION The above objects are achieved when the invented process and the invented device are used to coat a metallic wire with a lubricant for the purpose of imparting anti-friction proper¬ ties to a metallic wire. According to the invention, a lubri¬ cant is melted in connection with the substance being supplied to a dispensing container. By a lubricant is meant a substance or a mixture * of substances having lubricating effect . The melted lubricant is transferred to the applicator while con¬ trolling the flow of the melted lubricant from the dispensing container to the applicator, preferably by means of a step- less, controllable dispensing member. In the invented process, a solid lubricant is melted in connection with it being supplied to a dispensing container. The dispensing container is designed with a space in which the melted lubricant is received and collected. At or near the dispensing container, means for heating the dispensing container are provided. When starting the process, the , dispensing container is filled, while melting the lubri¬ cant, with melted lubricant to a suitable level, the working level, which is maintained essentially constant during the process, that is, the same amount, of lubricant as is consumed is supplied to the dispensing container by melting. The heat developed at or near the dispensing container melts the solid lubricant which thereby runs down into the dispensing con- tainer through one or more tubes, filling tubes, which open out below or on a level with the working level. Melted lubri¬ cant is supplied to the dispensing container from an accumu¬ lator container which is filled with solid lubricant and is placed near, preferably above, the dispensing container. The dispensing container is designed of a material with good thermal conductivity. The accumulator container and/or the dispensing container are/is provided with contact surfaces and other means such as flanges to obtain a good heat transfer from the heated dispensing container to the accumulator container and to fix these containers relative to each other. The accumulator container is provided with openings which are tightly connected to the filling tube of the dispensing con¬ tainer but is otherwise tightly sealed. Through the heat transfer from the heated dispensing container, the lubricant is melted in the accumulator container and runs through the filling tubes down into the dispensing container. When the working level has been attained, the level in the dispensing container will be maintained essentially constant since the sub-atmospheric pressure in the tight accumulator container ensures that only the amount which is consumed and obtained from the dispensing container will be filled from the accumu¬ lator container. Essentially all lubricant which is trans¬ ferred from the dispensing container to the applicator is coated on the metallic wire. In certain embodiments the accumulator container is provided with means for indicating the amount of lubricant in the accumulator container, for example in the form of a level glass. The dispensing container and the applicator as well as the channels which interconnect these are preferably maintained at a temperature exceeding the melting temperature of the lubricant. Usually lubricants are 'Used which have a melting temperature of 50 to 7Q°C. The temperature of the lubricant can be controlled to influence the viscosity of the melted lubricant and hence the result of the application of the lubricant. According to t.he invention, the wire is heated, prior to or in connection with the passage through the applicator, to a temperature exceeding the tempe¬ rature of the lubricant. In certain embodiments the holder, arranged around the appli¬ cator, and the dispensing container comprise interconnecting channels for transferring melted lubricant from the dispensing container to the applicator. To control the flow of melted lubricant from the dispensing container to the applicator, and to close and open the channels, respectively, for this flow, dispensing members, preferably stepless controllable dispen¬ sing members, are provided in certain embodiments of the invention. These members are, for example, arranged in the form of one or more valves in which a cone or a needle is closed against a seat . In one embodiment the valve is opened and closed, respectively, by controlling the position of the needle by an electromagnet. The flow through the valve is thereby controlled by signals which indicate the time during which the valve is opened and the time between the openings. In an alternative solution, a motor is used for controlling the opening/closing of the valve, whereby also the position of the valve in relation to the seat can be controlled for con¬ trolling the flow through the valve. Normally, the flow of melted lubricant to the applicator is controlled so as to correspond to a dosage of lubricant on the surface of the wire of lOmg/m-**** to lg/m^ wire surface. From the dispensing container, melted lubricant flows to the applicator This flow is preferably accomplished by designing the applicator of a fibrous, porous material which, by the capillary forces obtained when the applicator is compressed by a holder around the passing wire, sucks melted lubricant from the dispensing container. Since lubricant is consumed at the surface where the applicator contacts the wire, the contents of lubricant m the applicator is always lowest near the wire, whereby a driving force, a suction, arises for transport of lubricant to this area m order to maintain fluid balance in the applicator. In one embodiment of the invention, the appli¬ cator is designed with a wedge-shaped cutout which is arranged around the wire. A holder is arranged around the applicator. In clamped state, this holder has an inner diameter which is smaller than the outer diameter of the applicator in non- compressed state. When the holder is clamped, the applicator is compressed and the cutout is closed around the wire. This leads to a situation, at the centre of the applicator near the wire, whereby the applicator will make contact around the whole periphery of the wire with a resilient contact pressure. In certain embodiments, the holder comprises means for ensu¬ ring that the applicator is retained m the holder and is not pulled out of the holder by the wire. In a preferred embodiment of the invention, the melted anti¬ friction substance is distributed around the periphery of the wire in the applicator by means provided in the fibrous porous applicator which conduct and control the flow of the melted lubricant through the applicator. Preferably, a distributor in the form of a layer, impenetrable to the lubricant, is provi¬ ded with openings m the form of holes or slits whereby the flow of the melted lubricant from the channels of the holder to the wire is controlled to obtain the desired coating on the wire. The distributor layer is arranged inside the applicator and is made of a material which is not destroyed by the tempe¬ rature of the melted lubricant, preferably a plastic or a metal foil. BRIEF DESCRIPTION OF THE DRAWINGS The invention will be described in greater detail in the following with reference to the accompanying drawings and be exemplified by a preferred embodiment, wherein an enamelled winding wire for winding purposes is coated with a meltable lubricant of paraffin and/or wax type, which is the most common lubricant . Figure 1 shows all the important parts of the invention and its design. Certain parts are sectioned to show the method more clearly. Figure 2 shows the applicator 4 with distributors 7 and the wedge-shaped cutout 8. Figure 3 shows the accumulator container 13 with legs 19 and the lower level of the hole 20. DESCRIPTION OF THE PREFERRED EMBODIMENTS In the process for coating a metal wire with a lubricant as shown in Figure 1, a metal wire 2 passes through an applicator 4 where the wire is coated with melted lubricant. The melted lubricant is sucked by the capillary forces, which arise in the applicator 4 during the process, from a dispensing con¬ tainer 9. The dispensing container 9 is provided with a heater 10 which develops heat whereby the lubricant is melted while being supplied to the dispensing container. The dispensing container is provided with dispensing members 11, 12, 15, 16,. 17 for controlling the flow of melted lubricant which is sucked to the applicator 4. In Figure 1, a heater 10 is shown in the form of an electric resistor element which is controll¬ ed by a temperature regulator 24, but, of course, also other forms of controllable heat sources, such as coils traversed by hot water, may be used. To melt the lubricant and maintain it floating during the process, the temperature regulator 24 is set at a higher temperature than the melting temperature for the lubricant which is to be applied onto the wire 2, which has a constant rate through the applicator 4. The heat source 10 placed in the dispensing container 9 heats the entire device to a temperature which is higher than the melting temperature of the lubricant. For commonly occurring lubricants, The melting temperature is between 50 and 70°C. The heat source 10 has a strategic location in the dispensing container 9, which means that the channel 14 always has the highest and most uniform temperature to ensure at each time the flow of the dispensed lubricant in the system. The accumulator container 13 is filled with lubricant through the hole 20 in a special filler (not described) . After filling the accumulator container 13, it is to cool to room tempera¬ ture, which causes the lubricant to assume solid state. This allows the container to be handled in all situations, without considering the contents. By placing an accumulator container, filled with lubricant, on the dispensing container 9, heat will be transferred from the dispensing container 9 to the accumulator container 13 through the contact surfaces and the special flanges 19 with which the accumulator container is provided. These also have the task of fixing the container to the dispensing container 9. The heating of the accumulator tank 13 causes the lubricant to melt and to run down into the dispensing container 9 through the hole 20. When the working level 18, which is the same as the lowermost point of the hole 20, is attained, the level 18 * .will be constant and filled with the same amount as is consu- med. This achieved by the sub-atmospheric pressure which is generated in the accumulator container. In the described case, the container 13 contains lubricant for about 10 days. The accumulator container 13 has a level glass 21 which indicates when the container is to be replaced by a filled container. The dispensing container 9 is designed with a space 18 for lubricant and with channels 14, the task of which is to con¬ duct ■ lubricant to the applicator 4, which is placed in the holder 3. The holder may be mounted in a horizontal or a vertical position depending on the direction of the wire 2. The dispensing container 9 is provided with an adjustable fixing element 1, which makes it possible to adjust the device according to the wire 2. The dispensing member 11, 12, 15, 16, 17 consists of an elec- tromagnet 15, the armature 17 of which is connected to the needle 12 via an elastic sleeve 16 which causes the needle 12 to direct itself to the position of the valve seat 11. This means that a tight shut-off function can be obtained in a simple manner. The dispensing member is controlled by timed signals by means of a control device 25, the time during which the valve 12, 12 is open and the time between the openings. The holder 3 for the applicator 4 is equipped with a transport channel which is connected to the transport channels 14 of the dispensing container 9. The holder 3 has a circular hole in which the applicator 4 is compressed when the applicator 4 is applied in the holder 3. This compression leads to the creation of a resilient contact pressure at the centre of the applicator 4. To prevent the applicator 4 from being pulled along by the wire 2, a yoke 5 serves as a counter-support. The yoke 5 may be placed on both sides of the applicator 4 depending on the direction of movement of the wire 2. The holder 3 also has a slit which makes it possible for the wire 2 to placed at the centre of the holder 3 without being cut off. The holder 3 has a safety channel connected to the channel 6, which always guarantees a dispensed flow to the applicator 4, even if the lubricant should contain particles sealing the applicator 4. The applicator 4 is made of a fibre-composed sucking material which, with capillary properties, is capable of transporting li uid lubricant. The applicator 4 has a wedge-shaped cutout 8 so that it can be applied onto the wire 2 and, when the applicator 4 is placed in the holder , so that it can be compressed and create a contact pressure around the wire 2. To distribute the lubricant around the entire circumference of the wire 2, the applicator 4 is provided with distributors 7 which conduct and control a liquid substance, which in the described case is a melted lubricant. The distributor 7 is placed in cut sections in the applicator 4 and the lubricant is guided to the connections which are provided in the applicator 4 between the channel 6 and the wire 2. Connections may be provided in the distributor 7 through holes or slits, or as a space between two distributors. The distributors are made of a heat-resistant material in which the lubricant cannot pass. The material may advanta¬ geously be plastic or a metal foil. All the lubricant which is consumed will end up on the wire 2 since this is the only consumer in the device when the wire has one movement. Usually, the wire is coated with lubricant corresponding to a dosage of lubricant of from lOmg/m^ to lg/m2. The region nearest the wire 2 in the applicator 4 always contains least lubricant, which means that the lubri¬ cant strives to arrive at this region in order for the appli¬ cator 4 to achieve fluid balance, whereby the transport of lubricant from the dispensing container to the applicator is maintained.

Claims: CLAIMS 1. A method for imparting anti-friction properties to a metallic wire (2) , wherein the surface of the wire is coated with a lubricant by means of an applicator (4) in the form of a porous body comprising a fibrous material wherein the porosity of the bodv is completely or partially filled with a lubricant, characterized in that a lubricant is melted in connection with the substance being supplied to a dispensing container (9) and that the melted lubricant is transferred from the dispensing container to the applicator by the capillary forces in the pores of the applicator and a sub- atmospheric pressure which is generated when melted lubricant is consumed at the surface where the applicator contacts the wire. 2. A method according to claim 1, characterized in that the flow of melted lubricant to the applicator (4) is controlled in a stepless manner within an interval which corresponds to a dosage of lubricant of 10mg/m2- -lg/m***- * wire surface. 3. A method according to any of the preceding claims, characterized in that the applicator (4) is adapted to surround that part of the wire which during the passage is situated in the applicator and to make contact with the surface of this part of the wire with a resilient pressure. 4. A method according to any of the preceding claims, characterized in that the flow of melted substance through the applicator (4) is directed and distributed during the passage through the applicator, whereby the distribution of melted lubricant over the circumference of the wire is controlled. 5. A method according to one or more of the preceding claims, characterized in that the temperature is controlled for controlling the viscosity of the lubricant. 6. A method according to one or more of the preceding claims, characterized ir- that at least the dispensing container (9) and the applicator (4) are maintained at a temperature exceeding the meJ ng point of the lubricant. 7. A method acco * . ng to one or more of the preceding claims, characterized in _hat the wire (2) at least during the passage through the applicator (4) is maintained at a higher temperature than the applicator. 8. A method according to one or more of the preceding claims, characterized in that lubricant is supplied to the dispen¬ sing container (9) from an accumulator container (13) con¬ taining solid lubricant which is placed over the heated dis- pensing container whereby the lubricant is melted and supplied to the dispensing container. 9. A device for coating a wire (2) with a lubricant, said device at least comprising - an applicator (4) in the form of a porous body comprising a fibrous material with a porosity which is completely or partially filled with a lubricant, - a dispensing container (9) completely or partially filled with lubricant, and - means (6) for transferring lubricant from the dispensing container to the applicator, characterized in that the dispensing container comprises means (10) for heating the dispensing container and that the applicator is adapted such that the capillary forces in the pores thereof and a sub-atmospheric pressure, which arises in the applicator when lubricant is consumed, generate a suction which transfers lubricant from the dispensing container to the applicator. 10. A device according to claim 9, characterized by a stepless controllable dispensing member (11, 12, 15, 16, 17) to control the flow from the dispensing container to the applicator and hence the dispensing of coating on the surface of the wire . 11. A device according to claim 9 or claim 10, characterized in that the applicator (4) is provided with a wedge-shape ' d cutout (8) to be able to be applied around the wire (2) . 12. A device ^ according to claim 11, characterized by means (3) for compreεsing--the applicator (4) around the wire (2) and hence closing the cutout (8) and creating a contact pressure around the wire. 13. A device according to an> of claims 9 to 11, characterized in that the applicator is provided with means (7) for controlling and distributing the dosage of lubricant over the circumference of the wire. 14. A device according to claim 13, characterized in that the applicator comprises a distributor in the form of a shield (7) , arranged coaxially with the wire, which is made of a material which is impenetrable to the lubricant and is provi¬ ded with a number of passages in the form of holes or slits distributed over the surface of the shield, said shield (7) being arranged to control the distribution of lubricant over the circumference of the wire. 15. A device according to one or more of claims 9 to 14, characterized in that heat-transfer means (19) are adapted to transfer lubricant from the dispensing container to an accumulator container arranged adjacent to the dispensing con- tainer, whereby lubricant located in the accumulator container melts and is transferred to the dispensing container.

Inventors: ANDERSSON JAN, IVARSSON ROLAND, SOEDER ROLF, ANDERSSON, JAN, IVARSSON, ROLAND, SOEDER, ROLF
Applicants: ANDERSSON JAN, ASEA BROWN BOVERI, IVARSSON ROLAND, SOEDER ROLF, ANDERSSON, JAN, ASEA BROWN BOVERI AB, IVARSSON, ROLAND, SOEDER, ROLF
Application year: 1995
Main classification: B05C11
IPC codes: B05C1, B05C5, B05C11