Method For Continuously Progressively Deposition A Fluid On A Flexible Substrate Surface

Abstract

A method for applying a fluid having magnetic characteristics to a carrier tape in uniform parallel strips uniformly spaced apart and of symmetrical cross-section. The strips are applied to the carrier tape by deposition from a toothed rotatable cylindrical body. Fluid layers on the peripheral surfaces of the teeth contact the tape with the teeth moving at a higher rate of travel than the moving carrier tape. The teeth deposit the fluid in the spaced strips on the tape surface without contact between the peripheral tooth surface and the tape surface and in such a manner that the deposited strip assumes a symmetrical cross-section. The teeth are preferably spaced from each other circumferentially on the cylindrical body by a distance approximately equal to the circumferential peripheral dimension of the teeth.

Parent Case Text

This application is a continuation-in-part of the copending, now abandoned, U.S. application Ser. No. 875,727 filed Nov. 12, 1969 for "Method and Apparatus for Continuously Progressively Depositing a Fluid in a Flexible Substrate Surface."

Description

BACKGROUND OF THE INVENTION

The present invention relates to a method and an apparatus for automatically applying to a flexible carrier tape parallel strips of fluid having magnetic characteristics and which are uniformly spaced on the carrier tape surface. In particular the invention relates to the method and apparatus for providing parallel strips having uniform and symmetrical cross-section.

The tapes with the symmetrical magnetic units constitute a magnetic storage unit with a magnetic layer interrupted at constant intervals and are used for testing defects in sound recording apparatus among other uses.

The conventional method of producing symmetrical tapes is first to apply a magnetic layer by usual casting methods on to the carrier tape. Strips are then milled out by means of milling methods with the separation spacing and separation width between the magnetic units being transverse to the running direction of the tape. The time expended in the manufacture of such tape is wasteful, especially as always only one tape can be produced in the finished width. A very large dust formation occurs because of this aftertreatment involving removal of swarf. On account of the electrostatic charges which occur in the carrier tapes, which tapes usually consist of synthetic plastics foils, dust adheres very firmly to the said tapes.

The application of magnetic material to a flexible carrier tape in separated deposits, however, presents certain further problems. One of these problems in thus forming magnetic storage means is the undesirable electrical characteristics that result from forming storage means having strips of unsymmetrical cross-section. Not only must the strips be uniformly spaced by transverse of constant dimension, but also the strips must be of a constant width and have a cross-section in which the magnetic material is substantially uniformly described in symmetry from the centerpoint of the cross-section. Strips in which the magnetic material is disproportionately positioned adjacent one edge or the other are highly undesirable. Thus a symmetrical cross-section of uniformly spaced strips must be achieved, the method and apparatus for depositing the material in a fluid state to a carrier tape must operate continuously and without error.

SUMMARY OF THE INVENTION

Segments of a liquid of magnetic characteristics are applied to a continuous substrate from a plurality of separated peripheral surfaces on a succession of spaced teeth around the circumference of a rotatable cylinder. The cylinder rotates on its axis so that the separated tooth surfaces revolve and receiving increments of the liquid transfer the liquid in layers on these peripheral surfaces for deposition on the carrier tape which in turn is driven over a cylinder. The tooth peripheral surface passes in close adjacency to but without contact against the surface of the carrier tape. The fluid layer on each tooth peripheral surface is radially deeper than the spacing between the tooth periphery and the tape at the point of their closest approach. At the point of closest approach, the fluid layers contact the carrier tape surface and form deposits thereon while each tooth peripheral surface moving at a higher rate of travel than the carrier tape advances with respect to the position of its respective deposit on the tape surface. As the cylinder is long enough to extend transversely of the tape, the individual teeth extend along its length and the fluid deposits are parallel strips on the tape separated by spaces which result from the spacings between the teeth. The trailing edge of the tooth peripheral surface disengages from the strip deposit at a point central with respect to the parallel edges of the strip. Further the separation takes place with the clinging action of the liquid confined essentially to the central area of the deposited strip. The extent to which the tooth peripheral surface advances with respect to its respective deposited strip is a function of the width of the strip.

The dimension of the tooth peripheral surface circumferential of the cylinder is preferably equal to the circumferential spacing between the successive teeth.

OBJECTS OF THE INVENTION

The invention has for its object the production of a symmetrical tape, so as to guarantee a substantially quicker and dust-free production of the tapes.

It is another object of this invention to deposit a liquid magnetic material on a moving carrier substrate by rapid processing of the application apparatus whereby the magnetic units on the carrier substrate are formed in progressive manner and in timed relationship on the substrate surface.

According to the method of this invention, it has been found that the printing of the strips is particularly uniform in cross-section when the printing cylinder is operated at a peripheral speed which is higher than the running speed of the carrier tape.

It was found that, by comparison with the previously known rotary printing method, the advantage of a symmetrical formation of the cross-sections of the printed strips is assured.

The present invention avoids the strip becoming somewhat thicker on its rear side.

It was found that, using the method according to the invention, symmetrising tapes can be produced in large widths and lengths at speeds of some hundred metres per hour, without the quality of the tapes being deleteriously affected.

The prefabricated tapes can finally be cut to the necessary width and length for the customer.

Other objects and advantages of the invention will become apparent from a study of the following description taken together with the accompanying drawings in which:

FIG. 1 is a side view of the apparatus shown diagrammetrically;

FIG. 2 is a plan view of a tape section carrying symmetrical strips;

FIGS. 3 and 5 are diagrammatic side views of sections of tape formed by the present invention showing deposited strips in section;

FIG. 4 is a diagrammatic side view of a section of tape formed not according to the present invention, and

FIG. 6 is a side view in diagrammatic detail of part of the apparatus showing the teeth and the carrier tape at the area of closest approach.

Briefly, the apparatus and its method of operation comprise a dipping tank containing the fluid having magnetic characteristics. A film of the fluid is applied by a dipping cylinder to a printing cylinder. The film is formed by rotating the dipping cylinder so that it is partly immersed in the fluid bath in the tank and thus draws the fluid out on its surface. The film is formed by a doctor knife which strips the withdrawn fluid off the surface leaving the film. The printing cylinder has uniformly distributed around its circumference elongated parallel teeth with peripheral surfaces which are preferably equal circumferentially to the spacings between the teeth. The fluid of the film is transferred to the peripheral surfaces of the teeth without direct contact. The gap between the teeth peripheries and the dipping cylinder is adjusted to control the thickness of the layer of fluid applied to the teeth peripheries. The gap is generally about 0.1 mm according to the preferred embodiment of this invention and adjustments in a range can provide a final adjustment of the fluid layer thickness on the teeth while the doctor knife provides a coarser adjustment.

The layers of fluid are transferred from the teeth surfaces to a carrier tape passing over a guide cylinder. The teeth surfaces closely approach but do not touch the tape surface. Parallel strips of fluid are deposited on the carrier tape. To prevent the deposited strips from being assymmetrical, it is important that the tooth peripheral surface lead the respective deposited strip as the two move through the area from first contact to disengagement. The process of contact and deposition and disengagement is carried out so that at the moment of disengagement or interruption the trailing edge of each tooth is central of its respective deposited strip. Thus during the period of contact of the layers on the teeth with the carrier tape the teeth surfaces are advanced about half their circumferential dimension with respect to the position of the deposited strips on the tape. Thus the effect of the clinging action between the deposited fluid and the teeth and the layers on the teeth is confined and symmetry is achieved in the deposited strips.

The strips on the carrier tape are of constant widths and separated by constant intervals and have symmetry in cross-section.

DETAILED DESCRIPTION

Referring now more particularly to FIG. 1 of the drawings, a dipping cylinder 10, a printing cylinder 11 and a guide cylinder 12 are shown diagrammatically, arranged in vertical alignment and slightly spaced apart by gap 13 between cylinders 10 and 11 and gap 14 between cylinder 11 and cylinder 12. A carrier tape 15 moves across and around the guide cylinder 12. The printing cylinder 11 has a regularly toothed circumference formed by spaced apart teeth 16. A bath 17 of fluid containing magnetic characteristics wets the lower portion of the dipping cylinder 10.

The cylinder 10 rotating in the bath 17 drags fluid out which is formed into a film 18 on the cylinder surface by a doctor knife 19. The rotation of the cylinder 10 carries the film 18 up to the gap 13 where the teeth 16 of the rotating printing cylinder moving through the gap 13 in the same direction as the film 18 each pick up a layer 20 on peripheral surfaces 21 of the teeth 16. The surfaces 21 do not contact cylinder 10 but the cylinders 10 and 11 are set to rotate so that the gap 13 insures wetting of the surfaces 21 in the film 18. The radial thickness of the layers 20 on the surfaces 21 is controlled in part by the width of gap 13 and the thickness of film 18 in turn is controlled by knife 19.

The circumference of cylinder 11 is made up of the teeth 16 and spaces 22 between the teeth 16. Preferably the peripheral surfaces 21 and the spaces 22 are substantially equal in circumferential dimension. Thus in this embodiment the circumference of cylinder 11 is equally divided between the surfaces 21 and the spaces 22 between the surfaces 21. The layers 20 each coincide with the width of the respective teeth 16 and have a thickness on peripheral surfaces 21 at least equal to the width of gap 14. The layers 20 cling to the surfaces 21 until contact is made between the layers 20 and the tape 15. A substantial portion of the fluid of the layers 20 is deposited on the tape 15 as a result of the contact between the layers 20 and the tape while the teeth 16 pass close to but out of contact with the tape 15. Thus strips 23 are deposited separately on the tape 15 by the contacts of the layers 20 as the tape 15 moves over the guide cylinder 12. The strips 23 are carried away on the tape 15 for final processing.

The strips 23 as shown in FIGS. 2 and 3 are parallel and uniformly spaced apart, in the preferred embodiment. FIG. 4 illustrates the cross-sectional deformity characteristic of a deposited strip by a method other than the process of the present invention. FIG. 5, on the other hand, illustrates the cross-section of the product of the present invention.

The structure of the printing cylinder 11 and the carrier tape 15 and the method of depositing the strips 23 are shown in greater detail in FIG. 6 of the drawings. As seen in the diagrammatic illustration of FIG. 6, the teeth 16 carry layers 20 on their peripheral surfaces 21 so that the layers 20 approach the tape 15 from the right as the cylinder 11 is shown moving from right-to-left in a counterclockwise direction. The layer 20 on the rightmost tooth 16 is shown to have a radial thickness S.sub.A which is greater than gap 14 having the dimension S. The layers 20 contact the tape 15 which is also moving in a right-to-left direction and the layers 20 deposit a substantial portion of their liquid on the tape 15 as they move together. The lack of contact between the teeth 16 and the tape 15 and the fluidity of the liquid permit the teeth 16 to advance or lead the deposited liquid during this time of contact. This lead during this time of contact is one half the circumferential dimension of the tooth peripheral surface 21 shown in FIG. 6 as the dimension S. Thus at the point of disengagement of each tooth 16 from its respective strip 23 the trailing edge of the tooth 16 is approximately at the center of the strip 23. The point of disengagement is the area at which the liquid remaining on the tooth 16 and the liquid of the strip 23 become separated. This is illustrated in FIG. 6 by the trailing edge 24 of the leftmost tooth 16. As a result the clinging action of the liquid forms the neck 25 centrally of the deposited strip 23.

As described above the lead is achieved by moving the cylinder 11 periphery at a higher rate of travel than the carrier tape 15.

With varying sizes of deposited strips and teeth the rates of travel will accordingly vary. These relative rates of travel V.sub.1 the carrier tape and V.sub.2 for the printing cylinder can be calculated by the formula:

V.sub.2 = V.sub.1 + (.pi.r.sub.2 /n - K/2) 1/T I

where r.sub.2 is the radius of the printing cylinder 11, n is the number of teeth 16, K is the dimension of the space between the teeth and T is the contact time.

The contact time for each deposited strip 23 is the period of travel of the tape 23 from point where the deposited liquid first contacts the tape 23 to the point of disengagement. As the point of disengagement and the point of contact may be considered as symmetrically spaced from the Y-axis, the contact time is twice the period of travel from the point of contact to the Y-axis. The Y-axis is the vertical line through the axes of rotation of cylinders 11 and 12. The contact time T may be calculated by a mere geometric analysis based on the geometric configuration of FIG. 6, yielding: ##SPC1##

Inserting this value for T into formula I leads to the final result: ##SPC2##

where r.sub.1 is the radius of cylinder 12.

While the figures of the drawings are merely diagrammatic illustrating the parts and the steps of the invention, they represent actual practice in one embodiment of which, the radius of the printing cylinder can be 0.05m, the liquid layer 0.0003m, the clearance between the printing cylinder 11 and guide cylinder 12 0.0002m, the surfaces 21 and spaces 22 equally 0.039.

Calculation of the relative rates of travel, V.sub.1 and V.sub.2, for this embodiment by the above formula II, yielded the following result:

V.sub.2 /V.sub.1 = 1 + 0.1116

Therefore, the lead which is required for this specific embodiment is 11, 16 percent. Experiments were run to prove this theoretical result by varying V.sub.2 /V.sub.1 and simultaneously testing the cross-section symmetry of the applied strips. It turned out that indeed highly symmetric strips were produced when .DELTA.v/v was approximately 11 percent, which is in fairly good agreement with the theory.

The liquid suitable for deposition according to this invention is one which after solidification contains desired magnetic properties. Illustrative Examples of the preparation of a liquid for processing in the present invention are as follows:

EXAMPLE 1

220 g of a polyester produced from 3 moles adipic acid, 2 moles 1,4-butyleneglycol and 2 moles hexanetriol are dissolved in a solvent composed of 600 ml of chlorobenzene, 600 ml of ethylacetate and 100 ml of methylenechloride and are homogenized in a vibrating mill for 10 hours together with 1,000 g of highly magnetic y-Fe.sub.2 0.sub.3. 200 g of a 75 percent solution in methylenechloride of a triisocyanate produced by reacting 3 moles of toluylenediisocyanate with 1 mol of gylcerol or hexanetriol are added, followed by mixing for another 10 minutes. This liquid after deposition is condensed at temperatures of from 50.degree. to 80.degree.C to give a product having 39 percent by volume of magnetic material.

EXAMPLE 2

200 g of the polyester of Example 1 together with 2,200 g of highly magnetic ferrite products and 1,500 ml solvent composition as described in example 1 are ground for 8 hours in a vibrating mill. 180 g of a 75% solution of triisocyanate of example 1 are admixed. In the condensed product the proportion of the magnetic material is 60 percent by volume.

Claims

What is claimed is:

1. A method for depositing on a substrate foil an intimate mixture consisting of resin binder, solvent and magnetic particles therein so that the deposit has a symmetrical cross-section which comprises applying a layer of said fluid mixture to the peripheral surfaces formed on the circumference of a rotatable cylinder by teeth and teeth spaces, moving said substrate foil toward the rotatable cylinder around a guide cylinder and away from the rotatable cylinder without contact with the rotatable cylinder, moving said rotatable cylinder at a rate of travel which leads the rate of travel of the moving substrate by about 11 percent, moving said layer in predetermined timed relationship to and into contact with the moving substrate at said higher rate of travel than the substrate, depositing fluid mixture from each layer in the form of a deposit on the substrate surface, moving the peripheral surface at said relatively higher rate while the surface is in contact with the formed deposit on the substrate surface, moving the trailing edge of said peripheral surface to a separation from the formed deposit on the substrate surface at a point central of the lateral edges of the deposit, and shaping the distribution of fluid mixture in the deposits by a clinging action of fluid centrally of the deposit to provide symmetrical cross-section in the deposits.

2. The method as claimed in claim 1 wherein the liquid is an extremely intimate mixture of a liquid and magnetic Y-Fe.sub.2 0.sub.3.

3. The method as claimed in claim 1 wherein the film thickness on the cylindrical surface is controlled by the step of applying the film to the surface.

4. The method as claimed in claim 1 wherein the thickness of the layer is controlled by the spacing between teeth and the cylindrical surface.

5. The method of claim 1 wherein the point of first contact of each layer of liquid and the point of separation between the deposited liquid and the layer are symmetrically spaced from the vertical axis connecting the centers of the printing and guide cylinders.