ELECTROSTATIC LUBRICATION OF CUP-SHAPED CAN BODIES

Abstract: Electrostatic cup lubricating process and apparatus (15) in which cup-shaped can bodies (36, 37, 38, 39) are controllably conveyed in spaced relationship to each other through a lubrication application chamber (20). Lubricant is atomized to particle sizes permitting them to be gas borne and are introduced into such chamber so as to present the desired dispersion of charged lubricant particles about the travel path (11, 12, 13, 14) for can bodies (36, 37, 38, 39). The can bodies (36, 37, 38, 39) are electrically grounded individually during passage through such lubricant application chamber (20) so as to attract the charged particles resulting in the desired lubricant coating. Endless loop conveyor means (80, 81, 86, 87) are provided with adjustable features enabling a travel path (11, 12, 13, 14) to be adapted to differing dimension can bodies (36, 37, 38, 39).

Description: ELECTROSTATIC LUBRICATION OF CUP-SHAPED CAN BODIES This invention is concerned with electrostatic lubrication of the interior and exterior surfaces of cup- shaped sheet metal can bodies. In its more specific aspects, the present invention is concerned with in-line electrostatic lubrication of cup-shaped sheet metal articles during transport between work stations in a high speed can making operation wherein a plurality of can bod forming steps are carried out sequentially for continuous production of sheet metal can bodies. Development of deep drawn unitary can bodies fo use in the fabrication of two-piece sanitary cans is beco ing increasingly important commercially. In current deve opment work, not part of the prior art, it has been found that a need exists for proper lubrication of the cup-shap work product before entry into each work station. It is important objective that such lubrication be carried out high speed continuous line operations without substantial interruption of sequential can making steps. No apparat has been available for providing desired uniform lubrica- tion of c p-shaped can bodies for such purposes. • ' The present invention provides for uniform lub cation of interior and exterior surfaces of cup-shaped sheet metal work product for introduction into work stations in a continuous-line manufacturing process. A desired lubricant established in liquid form is atomized 97 " ' ' / to gas-borne particle sizes which are then electrically charged. A can body travel path is established through a lubricant application chamber providing controlled passage of can bodies in spaced relationship to each other while minimizing; conveyance means contact with such can bodies to avoid'blocking of lubricant particle deposition which is carried out by electrical grounding of such-can bodies. A desired lubricant coating is obtained, e.g. of the type which eliminates the need for washing of the can bodies subsequent to manufacture. Other advantages and contributions of the inven¬ tion are set forth in more detail in describing apparatus as shown in the accompanying drawings, in which: FIG. 1 is a schematic lay-out plan view of por- tions of a continuous can making line including in-line lubricating apparatus in accordance with the invention, FIG. 2 is a schematic perspective view, with portions cut away and omitted for clarity, of lubricant application apparatus in accordance with the invention, FIG. 3 is a schematic cross-sectional view, along a plane which is perpendicularly transverse- to-the direc- ' tion of movement of can bodies, of- lubricating .apparatus in accordance with the invention. • ' FIG. 4 is a perspective view, with portions cut away and omitted for clarity, of lubrication apparatus in accordance with the invention, FIG. 5 is a plan view of means for establishing travel paths through a lubricant application chamber in accordance with the invention, and FIG. 6 is a side elevational view of the appara- tus of FIG. 5 showing in addition the location of a lubri¬ cation apparatus and framing support structure. During can-making operations, sheet metal blanks are cut from continuous-strip flat rolled sheet metal, such as flat rolled steel having a protective coating or other suitable can making sheet metal stock. The blanks are formed into shallow cups, a step which can be carried out at the blanking station. Forming operations are cur¬ rently being developed and improved to enable economic production of extended-height sidewall unitary can bodies for use in the manufacture of two-piece cans to replace the conventional three-piece sheet metal cans used for food and beverages. Reshaping a flat sheet metal blank into a unitary can body with elongated side wall extending from its closed end so as to meet commercial requirements calls for improved deep drawing operations. Uniform -lubrication of work product surfaces for entry into each drawing or redrawing operation is an important aspect of these developments. The present invention provides for uniform interior and exterior surface lubrication with apparatus which can be located in high-speed can making lines in which cup shaped sheet metal work product is continuously moving from station to station. The invention facilitates such operations in providing desired lubrication without interference in the continuous movement of work product required for high speed manufacture of unitary can bodies. As shown schematically in FIG. 1, shallow cups from cup source 10 are directed along individual paths 11, 12, 13, 14 into lubrication apparatus 15 from which they continue along their individual travel paths to work station 18 at which, for example, a drawing operation is carried out. As described in greater detail later, the cup-shaped sheet metal can bodies are controllably con¬ veyed in spaced relationship to each other during passage through lubrication apparatus 15. Lubrication apparatus 15 includes a lubricant application chamber 20, as shown in FIG. 2, through which the travel path(s) for can bodies extend as shown in FIGS. 3 and 4. Lubricant application chamber 20 is defined by wall means, such as chamber bottom wall 21, side walls 22, 23, exit wall 24 and- entrance and top walls (not shown in the perspective view of FIG. 2) . As taught herein, such chamber defining wall means are free of electrical ground¬ ing and can be formed from non-electrically conductive plastic sheet stock such as polypropylene. In carrying out this invention lubricant par¬ ticles are generated in sizes permitting the lubricant particles to be borne and transported by a gaseous medium In the embodiment shown, lubricant in a desired liquid form, as supplied or established using heat, is provided in lubricant reservoirs 25, 26. This lubricant sump arrangement is established by sump walls such as side walls 27, 28 and central divider wall 30; such sump walls which define the reservoirs for lubricant are also free of electrical grounding. Individual atomizing means, suc as 32, 33, are associated with each lubricant reservoir. Liquid lubricant is drawn from each reservoir and atomize utilizing suitable atomizing means, pneumatic or ultra¬ sonic; such atomizing means per se are known and commer- cially available. Suitable heating means for controlling the temperature of the lubricant, such as heating element 34, are provided to controllably establish and/or maintai desired lubricant temperature. Plural lubricant reservoirs each with associate atomizing means along with gas-borne lubricant flow means as taught herein, provide an atmosphere of dispensed gas- borne lubricant particles contiguous.!to all surfaces ^ of the work product-during contre-lled passage through lubri- cant application chamber 20. Travel paths for can bodie such as 36, 37, 38 and 39 of F-IG. 3 are established in a unique manner which " contributes significant advantages. utilizing endless-belt loop means as shown in more detail and described in relation to FIGS. 4, 5 and 6. In the embodiment shown, the movement of gas- borne lubricant particles is controlled and directed to multiple and diverse portions of lubricant application ; chamber 20. For example, to opposite lateral sides of the work product travel paths through gas flow passages 40, 41 (FIG. 3) ; the latter are defined on opposite lateral sides of the lubricant application chamber by chamber walls 21, 22 in cooperation with passage walls 42, 43 respectively; similar gas flow passages (not shown) can be provided, e.g. at the leading end of chamber 20. The gas-borne lubricant particles enter the lubrication chamber 20 through apertures at a plurality of locations, such as 44, 45, 46 and 47, in chamber side wall 22, 23 as shown in FIG. 2. Aperture means are located for delivery of gas-borne lubricant particles into upper and lower portions of lubricant application chamber 20; e.g. above and below a horizontal travel path for work product as well as along the direction of movement between leading and trailing ends of such travel path. Location of Such aperture means is selected to provide the desired gas borne lubricant-particle atmosphere about the travel path.. The gas-borne lubricant particles are electri¬ cally charged by high voltage charging wires 48, 49 (FIG. 3) located above and below the can body travel path(s). As seen in FIGS. 2 and 4, a plurality of such charging wires are distributed along the direction of travel of ca bodies throughout the lubricant application chamber 20; such wires extend across substantially the full lateral dimension of such chamber. Electrostatic charging of gas- borne lubricant particles to desired voltage levels can b augmented at other locations between generation of the particles and their deposition on work product surfaces. The teachings of the invention provide means fo establishing travel paths through the lubricant applica¬ tion chamber including endless belt loop means which serv a plurality of functions. As shown in FIGS. 3 and 4, end less-belt loops are provided with a curvilinear exterior cross-sectional periphery which results in a tangential point contact with work product and minimizes blockage of or interference with deposition of lubricant particles. The can bodies are controllably conveyed and desired lubr cation is obtained with open ends of the can bodies directed downwardly, upwardly or horizontally. Flexible plastic tubular material, -such as- ~ poly urethane round belting, available from Eagle Belting Co. , Des Plaines, Illinois, is used for endless-&eϊt-loops. Th endless belts stabilize as well as support cup-shaped wor product during conveyance through chamber 20. For exampl in FIG. 3, loops 50, 51 contact edge portions at the downwardly-oriented open end of can body 39 to support its weight; endless loops 52, 53 contact the side wall of can body 39 at diametrically opposite sides to stabilize it in its upright position. FIG. 4 depicts means for electrically grounding can bodies during passage in spaced relationship through lubricant application chamber 20 using individual suspende ground contact means. Referring to the travel path define by endless-belt loops 50, 51, 52 and 53, can bodies 54, 55 and 56 are contacted by flexible metallic chains 58, 59, 6 and 61 during passage through chamber 20. Such flexible contact chains are grounded through wire 62, which is grounded to the support frame or otherwise; the other ground wires shown are similarly grounded. Exterior sur¬ faces of such elongated grounding wires are electrically insulated as they extend through the chamber 20 so as to avoid accumulation of lubricant particles and minimize cur rent loss. For example, ground wire 63 is covered by elec trical insulation 66 for such purposes. However, the work product contact chains are exposed to the extent required for individual electrical grounding of can bodies. Flexible chain linkages, e.g. of the key-chain type, provide desired flexibility and electrical contact. The periodic contact of such flexible chains with work product provides a self-cleaning action for lubricant whic might otherwise accumulate. The highly charged gas-borne lubricant particle are attracted to the grounded can bodies over their full interior and exterior surfaces because of the high poten¬ tial difference between the charged particles (up to abou 30,000 volts and higher) and the electrically grounded ca body. As seen in FIG. 3, endless-belt loop means con¬ trol passage of can bodies of a particular configuration along a selected travel path. For example, can body 39, and the other can bodies along its travel path, have a larger diameter than can body 38, and the other can bodi along the latter's travel path. Teachings of the presen invention relating to adjustable location of the endless belt loops, as described in more detail later in relatio to FIGS. 5 and.6, enable implementation of this feature which adds product flexibility among the travel paths fo production installations. Line speed along a travel path is controlled b drive means. Surface areas of the particular type of ca bodies in separate travel paths can vary within reasonab limits when using the same line speed for all of the tra paths while still accomplishing de.sired uniform lubricat Individual drive, means for the endless-belt loops enable differing line speeds for separate travel paths in can m ing lines equipped with work stations at the exit end. of the lubricant application chamber to accommodate the . can bodies; this further increases the range of can body sizes that can be handled in the separate travel paths through a common application chamber. Also, the quantitative supply of gas-borne particles can be regulated by gas supplied to the lubrican sumps. In a specific embodiment, gas flow from the atom¬ izing area to the deposition area is selectively adjusted to the speed of the line; that is, at line speeds above a selected median, the gas flow is increased; at line speeds below the selected median, the gas flow is decreased. Thus the movement or "flow rate" of lubricant particles into the chamber can be regulated by regulating gas, e.g. air, supplied to the lubricant sump(s). Such gas can be supplied as a part of the pneumatic atomizing and/or sup¬ plied or augmented by regulating gas supplied separately to the sump(s), as shown. Such separately supplied gas to the sump(s) can be regulated.to,control-,gas flow.from-.the atomizing area t the deposition area to supply lubricant particles in accordance with requirements of the line speed. An additional feature of the invention provides for grounding of the spaced can bodies through specially selected material for the endless-belt loop means. Elec¬ trical conductive particles, such as graphite, mixed "" witlT and embedded in the pliable plastic tubular belt material during manufacture provides sufficient electrical conduc¬ tivity for adequate grounding of the can bodies and dis¬ charge of electrical potential. In the embodiment of FIG. 3, the can body support loops 44, 45 are formed of such electrically conductive endless-belt loop material ( referred to as conductive polyurethane belting, available from Shingle Belt Co., Plymouth Meeting, Pennsylvania) and provide sufficient grounding through contact with a can body end; also, grounding can be further implemented by making endless loops 52, 53 electrically conductive so th a can body, such as 39, is grounded along its side wall. In the embodiment of FIG. 4, an insulated grou ing wire is positioned above each work product travel pa and extends in the direction of work product movement. Flexible metallic chains, exposed for electrical contact with each can body, are electrically connected to the ground wires. Four such flexible conductors are connect to each ground wire along each travel path in the embodi ment shown so that plural periodic grounding of each can body occurs during its controlled passage between entran port 70 and exit port 72 of the lubricant applicant appl cation chamber 20. Charging wires, such as 73, 74, 76 a 77, which extend laterally of the chamber, are positione to provide'charged particles dispersed about such- travel paths. Referring to FIG. 5, endless-belt loops for defining each travel path for continuous-line passage through deposition chamber means are shown in plan view along with pulley support means. For example, pulleys 78, 79 support endless-belt loops 80, 81 which contact the end of a can body (as shown open end down) for support thereof. Pulleys 82, 83 and 84, 85 support endless-belt loops 86, 87 which contact the side wall of a can body at diametrically opposite sides thereof. Different pulleys can be substituted to establis dimensionally differing travel paths and/or the pulleys ca be adjustably mounted along support shafts 88, 89. The number of travel paths can be varied, the width between support loops, and the height of and width between stabil- izing loops can be selected accordingly. The side elevational view of FIG. 6 shows the lubrication apparatus 15 in place on support framing mem¬ bers, such as 90, 92, which include means for adjusting th vertical position of such lubrication apparatus. Drive means including driveshaft 94 are provided as well as loop tension adjustment means 96, for the endless-belt loops. Groups of endless-belt loops which establish a travel path can be driven together. The present teachings also provide for individual loops-to be driven individually; for example, loops on diametrically opposite sides of a vertically oriented can body can be driven at slightly differing speeds to provide a slow rotational movement of a can body about its central longi¬ tudinal axis during passage through chamber 20. Data for a specific embodiment for carrying out I the invention are set forth below: Chamber 20 Longitudinal length (direction of can travel) 37" Lateral width (transverse to direction of movement of can bodies) 44" Height 24" Wall material (thickness) 1/2" (commercial polypropylene sheet) Lubricant Commercially available Petrolatum Heat to about 160° F. Atomizer Model #l/8-JJ-SS-J22D-SS Spraying System, Inc. Wheaton, 111 60187 Endless-Belt Loops Non-conductive 1/2" diameter poly- urethane tubing Electrically conductive (with dispersed graphite) 1/2" diameter con¬ ductive polyurethane tubing Charging: wire, about 30,000 volts and DC potential higher (raise voltage to highest potential practi¬ cable prior to leakage of current, arcing or exces- sive corona discharge) Line Speed (adaptable to commercial can making line practice) For Can sizes 211 x 400, typically 300 x 407 and 303 x 406 150 fpm Lubricant Particle Transport Gas Flow Enroute from Lube Sumps to Deposition Chamber about 4 to 5 cf (at about 15 ps 2 atomizers supplied at about 24 psia Can sizes are expressed in diameter and height; the 211 x 400 (2-11/16 diameter, 4" height) is a typical soup can, 300 x 407 is a typical pet food can, and the 303 x 406 is typically used for fruits and vegetables. While specific data including materials, dimen- sions and configurations have been set forth for purposes of describing the invention, modifications thereof can be made by those skilled in the art in the light of the pres¬ ent teachings. Therefore, for purposes of defining the scope of the present invention, reference shall be had to the appended claims.

Claims: 1. Apparatus for providing uniform lubrication of interior and exterior surfaces of cup-shaped sheet metal can bodies while continuously moving through a can making line comprising, in combination a lubricant source means providing lubricant in liquid form, atomizing means for converting such liquid lubricant into particles capable of being borne by and transported with a gaseous medium, a lubricant application chamber defined by wall means which are free of electrical grounding, means for directing movement of such gas-borne lubricant particles into the lubricant application chamber, means for electrically charging such gas-borne lubricant particles , means for supplying cup-shaped can bodies having a closed end wall and a side wall extending longitudinally therefrom symmetrically with a can body central longitudinal axis to define an open end longitudinally opposite to such closed end, and conveyance means for controlling continuous-line passage of such can bodies in spaced relationship to each other through such lubricant application chamber, such conveyance means defining, a travel path along which such can bodies are electrically grounded . individually during passage through such lubricant application chamber. 2. The apparatus of claim 1 in which such lubricant source means includes a plurality of lubricant reservoir means each with an associated atomizing means for supplying such lubricant particles. 3. The apparatus of claim 1 in which such means for directing movement of such gas-borne lubricant particles includes gas flow passage means between such lubricant source means and such lubricant application chamber. 4. The apparatus of claim 3 in which such gas- flow passage means directs gas-borne lubricant particles into such lubricant application chamber at a plurality of loca- tions positioned in relation to such travel path for can bodies to provide an atmosphere of dispersed gas-borne lubricant particles about such travel path within such lubrication chamber. 5. The apparatus of claim 2 in which such means fo directing gas-borne particles into such lubricant application chamber includes passage means from each of such plurality of reservoir means into such application chamber. 6. The apparatus of claim 1 in which the means for electrically charging such gas-borne particles are located within such lubricant application chamber. 7. The apparatus of claim 6 in which such means for electrically charging lubricant particles are positioned in relation to such travel path for can bodies to provide an atmosphere of dispersed electrically charged gas-borne lubriσ-ant particles about such travel path. 8. The apparatus of claim 1 in which such conveyance means defines a substantially horizontal travel path through such application chamber in which such can bodies are supported at their longitudinal ends and stabilized along their side walls to maintain such can bodies with their central longitudinal axes substanti- ally vertical during passage through such application chamber, such means for directing movement of gas-borne particles into such application chamber directs such particles above and below such horizontal travel path, and such means for electrically charging gas-borne particles are located above and below such horizontal travel path. 9. The apparatus of claim 1 in which such convey- ance means includes elongated endless-belt means presenting a curvi- linear peripheral surface providing tangential point_σontact with such can bodies so as to minimize the area of contact with such can bodies during their passage through " such _ lubricant application chamber. 10. The apparatus of claim 1 in which-such"can bodies are electrically grounded by flexible electrical 3 conductors located along such travel path so as to periodic- 4 ally contact and ground such can bodies during passage 5 through such application chamber. 1 11. The apparatus of claim 8 in which such can 2 bodies are electrically grounded by flexible electrical 3 conductors supported in spaced relationship along such hori- 4 zontal travel path from above such vertically-oriented can 5 bodies for contacting and grounding can bodies individually 6 a plurality of times during passage along such travel path. 1 12. The apparatus of claim 10 in which such 2 flexible electrical conductors are suspended from grounding 3 wires which are electrically insulated between such flexible 4 electrical conductors. 1 13. The apparatus of claim 9 in which such 2 elongated endless-belt means comprises plastic tubing. 1 14. The apparatus of claim 12 in which such 2 plastic tubing includes electrically conductive particulate 3 material for grounding ' such can bodies through such convey- 4 ance means during passage through such application chamber. y • 15. The apparatus of claim 1 in which such convey- 2.; ance means comprises 3 elongated tubular-configuration endless loop means — providing continuous-line passage through such lubricant - 5 application chamber, - 6 such endless loop means being controllably posi- 7 tioned for travel through such lubricant application chamber by support me-ans located at opposite longitudinal ends of the travel path through such lubricant chamber. 16. The apparatus of claim 15 in which such support means include J rotatable means which are adjustable to provide a travel path which can be adjusted for separate runs through such application chamber to accommodate can bodies of differing external dimensions. 17. Method for providing uniform lubrication of interior and exterior surfaces of cup-shaped sheet metal can bodies while continuously moving through a can manufacturing line comprising, in combination providing a source of lubricant in liquid form, atomizing such liquid lubricant into particles capable of being borne by and transported with a gaseous medium, providing a lubricant application chamber defined by wall means which are free of electrical grounding, directing movement of such gas-borne lubricant particles into the lubricant application- chamber, electrically charging such gas-borne lubricant particles, __ ' - . ' " ■ ■ supplying cup-shaped can bodies having a closed end ' wall and a side wall ex-tending, longitudinally therefrom symmetrically with. . a can body central longitudinal axis to define an open end longitudinally opposite to such closed end wall, . . - ' ■ '- ' - - providing a travel path for movement of such can bodies through such lubricant application chamber, controlling continuous-movement passage of such can bodies into, through and out of such lubricant application chamber with such can bodies being spaced in relation to each other during such passage, and electrically grounding such can bodies during passage through such lubricant application chamber so as to attract such electrically charged particles to interior and exterior surfaces of can bodies during such continuous- movement passage . 18. The method of claim 17 including controlling the temperature of such lubricant prior to atomi zing. 19. The method of claim 17 in which the step of directing movement of gas -borne- lubricant particles into the lubricant application chamber includes quantitatively controlling the flow rate of such particles into such chambe -==..- 20. The method of claim 19 in which the step of controlling-continuous-movement passage of can bodies through such application chamber includes controlling the rate of movement ©f _s-uch~ can bodies through such chamber. 21. The method -of claim 20 in which control of th quantitative flow rate of gas -borne particles is coordinated with the control of - ate of movement of can bodies through such application chamber to provide for uniform surface lubrication at variable line speeds . . 22. The method of claim 17 in which such step of electrically grounding such spaced can bodies is carried out a plurality of times along such travel path during passage through such lubricant application chamber.

Inventors: BRAY JAMES A, BRAY, JAMES, A.
Applicants: WEIRTON STEEL CORP, WEIRTON STEEL CORPORATION
Application year: 1985
Main classification: B05B5
IPC codes: B05B5, B05B15, B05D1, B05D5, F16N7