COATING DIE

Abstract: A coating die assembly is adapted to apply a number of materials onto a moving web (12) from a single coating slot (16) by the use of a movable cam (25) in the die assembly to alternately connect the coating slot (16) to one or the other of a pair of inlet ports (22) and seal the other port (22). Movment of the cam thus facilitates rapid change of materials from the coating slot (16) onto the web (12).

Description: Technical Field This invention relates to an improvement in a pressure fed coating die, and in one aspect, to an improved multi-component coating die which will afford the coating of different materials successively lengthwise on a web without interrupting movement of the web. It has been desirable in the past to be able to coat a stripe or coat a product in the machine direction of a moving web and then to either interrupt the coating or to apply a different coating to the web down stream from the first coating in the same general area on the web. Such systems have required, however, the interruption of the coater and a changing of the material in the coating die to be able to apply the next coating. One such coating die assembly is disclosed in US-A-4025671 which has a die assembly comprising a die body having a coating orifice opening through an exterior surface adapted to be positioned adjacent the web to be coated, a cavity communicating with the orifice and an inlet port communicating with the cavity. Disclosure of Invention The present invention provides an improved multi-material pressure fed coating die which will permit the application of two different compositions in the same down web stripe, multiple cross web stripes in multiple compositions in the down web direction, and intermittent stripes of the same or different compositions. According to the present invention there is provided a coating die assembly for coating a web, said die assembly comprising a die body having a coating orifice opening through an exterior surface adapted to be positioned adjacent the web to be coated, having a cavity communicating with said orifice, and having an inlet port communicating with said cavity, characterised in that said die body has a pair of inlet ports, a cam within said cavity and having recesses for defining with said die body a pair of manifolds, said cam being movable relative to said die body between a first position with a first one of said manifolds communicating between a first one of said inlet ports and said coating orifice and a second one of said manifolds sealed from said coating orifice, and a second position with the second one of said manifolds communicating between a second one of said inlet ports and said coating orifice and the first one of said manifolds sealed from said coating orifice, and means for moving said cam between said first and second positions. Preferably the die assembly also has a pair of bypass ports and in the first position of the cam the second one of the manifolds is that is sealed from the coating orifice communicates between the second one of the inlet ports and one of the bypass ports, and in the second position of the cam the first manifold that is sealed from the coating orifice communicates between the first one of the inlet ports and the other one of the bypass ports. Also, the die body of the die assembly can have a plurality of spaced coating orifices opening through the outer surface and communicating with the cavity and a plurality of spaced inlet ports communicating with the cavity. The cam can have a plurality of spaced recesses defining with the die body a plurality of manifolds with a different pair of the manifolds adjacent each coating orifice, with a first one of the manifolds adjacent each coating orifice communicating between a first one of the inlet ports and that coating orifice and a second one of the manifolds adjacent that coating orifice being sealed from that coating orifice in the first position of the cam, and the second one of the manifolds adjacent that coating orifice communicating between a second one of the inlet ports and that coating orifice with said first one of the manifolds sealed from that coating orifice in the second position of the cam. Brief Description of Drawing The present invention will be further described with reference to the accompanying drawing wherein: Figure 1 is an end view of a coating die body constructed according to the present invention; Figure 2 is a bottom view of the assembled coating die of the present invention; Figure 3 is a top plan view of the coating die; Figure 4 is a side elevational view of the coating die; Figure 5 is an end view of the assembled coating die; Figure 6 is a diagrammatic illustration of an end view of the coating die; Figure 7 is a second diagrammatic view of the coating die of the present invention; Figure 8 is a plan view of a web coated with the coating die; and Figure 9 is a detailed view of a cam for the coating die as illustrated in Figures 1-4. Detailed Description The coating die assembly of the present invention permits a single coating composition to be interrupted abruptly or multiple compositions to be applied successively along a moving web in the same coating area or multiple stripes of separate coating materials transversely of a web and along the length of the web. Figure 1 discloses an end view of the die assembly having a block shaped die body 10 formed with an external lower coating surface 11 across which a web 12 is drawn to receive onto that web various materials. The body 10 is formed with two projections 13 at one end and a transversely extending cylindrical bore forming a fluid chamber 15 in the body. The chamber 15 communicates with a slotted coating orifice 16 formed in the face 11 of the die body 10 from which the coating material or composition can flow to coat the web 12. The orifice 16 may comprise a single orifice or spaced orifices along the transverse dimension of the die, depending on the number of stripes to be applied to the web. As illustrated the orifice 16 is a thin slot. A plurality of inlet ports 22 are directed from the side walls of the coating die body into communication with the chamber 15 and a series of exit or outlet ports 23 communicate with the chamber and the upper surface of the body 10. The inlet openings each communicate with a constant displacement metering pump (not shown) to assure precision coating weight control for the solution to be coated from an orifice 16 onto the web 12. As shown in Figure 2 and 5, an operator is used to control the position of a cam 25 disposed in the fluid chamber 15. The cam 25 is disclosed in Figure 9 and described below. The operator comprises a double acting fluid cylinder 17 pivoted on trunnions 18 which are journalled in a bracket 19. The piston rod of the cylinder 17 is fixed to a clevis 20 which is coupled by a pin to a radial arm 21 extending diametrically through one end of the cam 25 and held by a set screw. Operation of the cylinder 17 will oscillate the arm 21 and cam 25 through an arc defined by adjustable stops 24 threaded through projections 13. Various mounting brackets are shown to support the cylinder 17 on the die body 10 and the assembled coating die adjacent the web transport. As shown in Figure 9, the cam 25 has ends 26 and 27 which conform to and rotatably fit within the chamber 15. The end 26 has a portion of greater diameter than the chamber 15 to restrict axial movement of the cam in one direction. Between the ends of the cam may be formed coaxial baffles 28 which separate cut out areas forming pairs of manifolds 31-32, 33-34, and 35-36 on opposite sides of the axis of the cam 25. The cam 25 thus has a pair of manifolds adapted to communicate with each coating slot 16, which manifolds are separated by a partition 40 formed by walls along chords of the elongate cylindrical die cam. Each partition 40 separates a pair of manifolds and extends from the circular periphery on one side of the axis to the periphery on the opposite side forming two land areas 42 and 44. The land area 42 can close one or the other of the spaced bypass ports 23. The land area 44 can close the coating slot 16 or afford communication between one manifold and the coating slot 16. The land area 44 will seal the one manifold from the coating slot and the land area 42 will allow free communication of the one manifold with a recirculating bypass port 23. Rotation of the cam 25 about its axis then reverses the position of the cam to connect the other of the manifolds with the die orifice 16 and connect the first manifold with the bypass port 23. The land areas 42 and 44 may follow a helical path along the length of the cam, be staggered circumferentially, or have other positions with respect to the coating openings. The cam end 26 has a hole 41 to receive the arm 21 and the end 27 has a peripheral groove 43 to receive a retaining clip or washer to retain the cam against axial displacement. The die illustrated in the drawings comprises three coating orifices 16 positioned transversely of the web 12 and six manifolds in the cam. Each of the inlet openings 22 can be connected to a separate coating composition to permit six different coating compositions to be coated along the length of the web with three of the coatings being applied simultaneously as illustrated in Figure 8. As illustrated therein, coatings A, B, and C can be applied and then the cam 25 is rotated during continued web movement to apply coatings D, E, and F. Only residual amounts of coatings A, B, and C would appear in the areas of coatings D, E, and F because of the residual material left in the coating slot 16 between the fluid chamber and the position where the slot communicates with the surface 11 on the die body 10. The cam and die body illustrated has three coating slots whereas there could alternatively be one with a pair of manifolds, or the cam could be divided at a baffle 28 and each end of the cam could rotate independently to increase the number of patterns of coating materials which could be applied to a web. The die body illustrated has the surface 11 within 1.52 mm (0.060 inch) of the fluid chamber 15 and the slots have a width in the web direction of 0.25 mm (0.010 inch). The shape, length, and spacing between coating openings can vary.

Claims: A coating die assembly for coating a web (12), said die assembly comprising a die body (10) having a coating orifice (16) opening through an exterior surface (11) adapted to be positioned adjacent the web (12) to be coated, having a cavity (15) communicating with said orifice (16), and having an inlet port (22) communicating with said cavity (15), characterised in that said die body has a pair of inlet ports (22), a cam (25) within said cavity (15) and having recesses for defining with said die body (10) a pair of manifolds (31, 32), said cam (25) being movable relative to said die body (10) between a first position with a first one (31) of said manifolds (31, 32) communicating between a first one of said inlet ports (22) and said coating orifice (16) and a second one (32) of said manifolds (31, 32) sealed from said coating orifice (16), and a second position with the second one (32) of said manifolds (31, 32) communicating between a second one of said inlet ports (22) and said coating orifice (16) and the first one (31) of said manifolds (31, 32) sealed from said coating orifice (16), and means for moving said cam (25) between said first and second positions. A die assembly according to claim 1 wherein said die body (10) has a pair of outlet ports (23) and in said first position of said cam (25) the second one (32) of said manifolds (31, 32) communicates between said second one of said inlet ports (22) and one of said outlet ports (23), and in said second position of said cam (25) the first one (31) of said manifolds (31, 32) communicates between said first one of said inlet ports (22) and the other one of said outlet ports (23). A die assembly according to claim 1 wherein said die body (10) has spaced coating orifices (16) opening through said outer surface (11) and communicating with said cavity (15), and a plurality of spaced inlet ports (22) communicating with said cavity (15), said cam (25) has a plurality of spaced recesses defining with said die body (10) a plurality of manifolds (31,32;33,34;35,36) with a different pair of said manifolds (31,32;33,34;35,36) adjacent each coating orifice (16), a first one of said manifolds (31;33;35) adjacent each coating orifice (16) communicating between a first one of said inlet ports (22) and that coating orifice (16) and a second one of said manifolds (32;34;36) adjacent that coating orifice (16) being sealed from that coating orifice (16) in the first position of said cam (25), and a second one of said manifolds (32;34;36) adjacent that coating orifice (16) communicating between a second one of said inlet ports (22) and that coating orifice (16) with said first one of said manifolds (31;33;35) sealed from that coating orifice (16) in the second position of said cam (25).

Inventors: MAIER, GARY W. C/O MINNESOTA MINING AND
Applicants: MINNESOTA MINING AND MANUFACTURING COMPANY
Application year: 1988
Main classification: B05C5
IPC codes: B05C5, B05C11, B05B12