US3545495A

US3545495A - Tubing

Info

Publication number: US3545495A
Application number: US730235A
Authority: US
Inventors: Rocco Falcomato; Jacob A Almouli
Original assignee: Niemand Bros Inc
Current assignee: Clarcor Inc
Priority date: 1968-05-20
Filing date: 1968-05-20
Publication date: 1970-12-08
Anticipated expiration: 1987-12-08
Also published as: DE1925687A1; FR2008895A1; GB1204645A

Description

United States Patent Inventors Rocco Falcomato [56] R f e e Cit d Brooklyn; UNITED STATES PATENT Jacob A.Almouli, Forest Hills, New York 3 037 529 6/1962 H S A I No 730 235 ancl l38/l44 3,080,893 3/1963 Craycraft 138/144 May 1968 3 267 968 8/l966 Foll m1 138/141 Patented Dec. 8, 1970 1 Assignee Niemand Bros. Inc. Primary Examiner-Laverne D. Geiger Elmhurst, New York Assistant ExaminerRichard J Sher a corporation of New York Attorney Kane, Dalsimer, Kane, Sullivan and Kurucz TUBING 7 Claims, 4 Drawing Figs.

US. Cl. 138/144,

l6l/2l4, 161/227 ABSTRACT: A dimensionally stable tube, particularly for use Int. Cl. Fl6l 9/16 with a voice coil, formed of three layers, a first layer having Field ofSearch 138/144, structural integrity and dimensional stability, 3 second layer ymi g acting synergistically with the first to retain the structural inl6l/227, 214 tegrity.

Cl/T L UI l In various applications tubular members of exceptional dimensional stability are necessary. As a particular example, a voice coil tubewhich actuates the speaker diaphragm of a speaker assembly cannot properly perform its function without being formed as an almost perfect hollow cylinder, and maintaining this configuration throughout its life. In most speaker assemblies, such as in radio, television, and high fidelity phonograph speakers, this voice coil tube isconnected to the diaphragm, and a coil of wire is wrapped around the voice coil tube, the coil carrying impulses from the electronic circuitry of the system. These electrical impulses are transformed into'the sound emanating from the speaker through the action of the voice coil tube on the diaphragm. If the tube assumes a shape which'is slightly out of round, the result is a distortion in the sound produced by the speaker.

Two methods have previously been employed in the prior art to form these voice coil tubes, both methods suffering certain deficiencies as will bernorefully set forth below. In the first method, a blank was cut from a relatively thin sheet of aluminum; This aluminumblank was bent into the hollow cylindrical configuration to form the voice coil tube. However, the formation of a perfect circle was extremely difficult and, as it was almost impossible to reform the blank, there was a great deal of waste material.

The second method employed in the prior an involved the spiral winding of a plastic-impregnated paper. The resulting tube lacked both dimensional and water stability. The plastic impregnation, if kept withirrthe proper limits such that the ultimately formed tube could function in the desired application, did not impart sufficient water resistance to the paper, or stiffness to the structure,,to provide the tube with the necessary properties. I In accordance with the. present invention, we have developed a structure for av oice coiltube which can be formed economically andwhich has dimensional stability and structural integrity, even when subjected to heat and highatmospheric humidity.

SUMMARY THE INVENTION In accordance with.the,-present invention, we have found that a dimensionally stable tube, particularly for use wit voice coils, can be formed as a two layer structure.

The first layer of the tube'is a dimensionally stable material which is relatively stiff and resilient. l

Several properties are required ofthe second layer. First,it must have the type of surface which aids in bonding of the wire coil to be wrapped around the ultimately formed tube. Secondly, it must be heat stable and relatively moisture resistant. Because of these latter two properties, it aids, synergistically, in making the overall tube dimensionally stable.

The tube can have a third layer, particularly when it is used as a voice coil tube, of a thermosetting resinous layer. While each of the layers must be thin, particularly when the structure isv to be employed as a voice coil tube, this last, thermosetting layer is extremely thin. The, primary function of this outer layer is to provide a surface which is compatible with the insulation of the wire which is coiled about the tube. It must also cover the second layer as an aid in providing stability of the overall structure in the presence of atmospheric humidity.

The overall structural integrity and dimensional stability of the tube are greatly enhanced when the first two layers are formed by spiral winding.

BRIEF DESCRIPTION OF THE DRAWINGS In the accompanying drawings:

I FIG. I shows a section of a tube having the structure of the 2 FIG. 4 is a speaker assembly including a portion of the tube of FIG. 1, cut to size for use in the application.

DESCRIPTION or THE PREFERRED EMBODIMENTS As previously indicated,'the tube of the present invention is preferably formed by a spiral winding operation. Such an operation, and i the equipment necessary, are generally described in the copending application of Rocco Falcomato and Zdenek Krajca, Ser. No. 554,287, filed May '26 1966, now abandoned for Plastic Tubes and Method of Making the Same," and assigned to the same assignee as the present invention. That portion of the referenced copending application is hereby incorporated, by reference. r

In general, the spiral winding operation involves the use of a smooth mandrel having a diameter equal to the'desired inner diameter of the tube to be formed. The first layer of spirally wound material is wrapped around the mandrel and is driven by an endless belt. Preferably, the side of the strip which comes in contact with the mandrel is coated with an inert lubricant in order to assist movement of the strip on the mandrel. The second spirally wound layer is then placed over the first and the composite structure is drivenby an endless belt. The undersurface of the second spirally wound layer can be coated with an adhesive prior to application to the first formed tube, in order to promote adhesion between the two layers. Similarly, eachof thesurfaces which is to be joined can be coated with an adhesive prior to winding of the second layer.

In accordance with the present invention, a tube 1 is formed in accordance with aspiralwinding operation similar to that described above. A first layer 2 of the dimensionally stable, stiff and resilient material is first wrapped onto the mandrel. This layer 2 thus forms the inner layer of the formed tube. The width of the tape used to form this layer is generally between 1% inches and 3 inches, but is preferably between about 1% and] /2 inches. The diameter of the mandrel on which the first layer is placed, and thus the inner diameter of the formed tube is generally from about it to 3 inches. Preferably, for use in voice coil tubes, this inner diameter is from about a inch to 1% inches. I

The angle of approach of the tape of this first layer, with respect to the mandrel, is generally from about 25 to but most preferably is at about 45. This angle of approach, obviously determines theangle 3 of the various courses of the material within the tube. The tension placed on the tape as it is wound onto the mandrel is generally between about 4and 10 pounds, and the degree of tension varies directly with the ply and width of the layer being wrapped. The layer is formed on the mandrel by butt joining the successive courses of tape, without adhesive.

The tape employed can be varied in thickness from about I to 2 mils. This will be related to the overall dimensions of the tape to be described later. The materials employed in forming this layer of the tube, as previously described, must be relatively stiff and resilient. Materials which are particularly suited generated in operation of a voice coil tube, to make them useful in this structure.

The second layer 4 of material for the tube is also spirally wound onto the mandrel, over the first layer 2. The tape dimensions and conditions of wrapping are the same as those set forth above with respect to the first layer of the tube. However, the thickness of the film used for the second layer generally varies from about 2 mils to 3 mils. The second layer 4 of tape is so wound onto the mandrel that the butt joints do not overlap and, preferably, the butt jioints of the second layer fall in the center of the courses of the first layer. As with the first layer, the butt joints are formed without adhesive.

Prior to winding the second layer 4 onto the first layer 2, an

.1 adhesive Sis appliedto'the undersurfaceof the tape forming the second layer 4. The presence of thisadhesive layer 5 is clearlyindicated in theenlarged view of FIG. 2. The type of adhesive employed varies with the use to which the tube will be put. Forexample, when the tube is subjected to a heat which is not considered excessive, i.e., not more than about a polyimide adhesiveis:

12 percent Polyimide resin: and

88 percent Mixture of methyl pyrrolidine and acetamide.

For example, DuPont Pyre ML RK-692 can be employed in this application.

The purpose of the second layer 4 is to provide resistance to heat andhumidity and also to provide a surface for bonding of electrical elements to the tube. Preferred materials for use in this layer arethe Kapton film, described with respect to the 1 first layer 2, and. a tape formed of Nomex. Nomex is a polyamide paper, and thus constitutes a fibrous material extremely resistant to high temperatures. Q j in general, if the first layer 2 is formed of an aluminum film,

then the second layer 4 is formed of a Kapton film or Nomex patible with the electricalelements to be bonded.

In general, these electrical elements comprise an electrical wire which is coated with an insulating layer of a synthetic resin. Thus, the preferred material for the layer 6 is a crosslinked synthetic resin system, of the same type as that employed for the wire insulation. For example, the material can be a phenolic resin.

As previously noted, the only requirement for the thermosetting resinous layer 6 is that it cover the second layer 4. Thus, it is applied in as thin a layer as possible to accomplish this purpose. In general, the thickness of this thermosetting layer 6 should be about mil.

For use in voice coil tube applications, the overall thickness of the tube should generally be from about 3 to 6 mils, depending upon the use towhich the tube is to be put. Depending upon the specification of tube thickness, this thickness must be maintained within a tolerance of about i 1% mil, and the internal diameter of the tube must be maintained to a tolerance of about :L l milsSuch fine tolerances can best be maintained by formationof a structure as described in this invention.

Employingthe structureof this invention, the formed tube inherently possesses the desired properties of structural integrity and. dimensionalv stability. If the wall thickness is reduced below the desiredlevel, then there is insufficient structural integrity, while if the wall is thicker than that specified, then excessive heat is generated in operation, because of, the excessive power requirements to generate sound.

paper, while if the first layer is formed of a Kapton film, then the second layer is formed of Nomex paper. However, in certain special applications, both layers can be formed of Kapton The following example illustrates preparation of a tube having the structure of the present invention. The tube was formed with an internal diameter of 1.5 inches, a wall thickness of 3'mils, and a length of 18 inches. Thus, the man drel employed for formation of the spirally wound tube had a diameter of 1.5 inches. One layer of 1 mil thick aluminum foil film having a hardness of 11-18 was wrapped around this mandrel asa first layer. A tension of about 6 pounds was maintained on the tape during winding and the angle of approach was 65. The layer was coated with a polyester based adhesive,

having the formula previously set forth, and this adhesive was brought to atacky state by partially vaporizing the solvents from it.

The second layer, overwrapped on the. first, was a 2 mil thick, Nomex paper tape having a width of l inches. The underside of this layer was also coated with a polyester based adhesive which was partially dried, again, to bring the adhesive to the tacky state. The tension on this tape, during application, was also about 6 pounds and its angle of approach was the same as that of the aluminum foil film. The two adhesive sides were applied in juxtaposition to bond the first aluminum foil film to the second Nomex paper film, with the butt joints of the Nomex lying between those of the aluminum foil.

The wound tube was thenpassed through a metering coating applicator where a phenolic based resin was deposited on the surface in an amount sufficient to cover the N omex layer.

This phenolic resin was then dried. As the tube was removed.

from the mandrel, a flying cutoff saw cut the tube in two inch lengths, suitable for use as a voice coil tube.

The application of the shorter lengths of the tube for usein Wrapped around the tube, in several layers, is an insulated wire 9 which transmits electrical impulses from the electronic system of a radio, television set, high fidelity phonograph, or other similar system.

Thus, an improved structure for a tube having structural integrity and dimensional stability has been shown. These tubes are superior to those of the prior art and can be formed in a more facile manner.

We claim:

1. A tube having structural integrity and dimensional stability and formed of:

a. a first layer of a film of a material selected from the class consisting of hard aluminumand polyimide;

b. a second layer formed from a film of a material selected from the class consisting of poly'amide and polyimide; and

c. a thermosetting phenolic resinous layer.

2. The tube of claim 1 wherein the first and second layers are spirally wound.

3. The tube of claim 1 wherein the successive courses of the spirally wound material are butt joined in the absence of adhesive, and the butt joints of the second layer lie within the coursesof the first layer.

4. A tube having structural integrity and dimensional stability for use in a voice coil attached to the diaphragm of a sound speaker comprising:

a. a first spirally wound layer formed from a film of a material selected from the class consisting of hard aluminum and polyimide, wherein said film has a thickness of from 1 to 2 mils;

b. a second spirally. wound layer formed of a film of a material selected from the class consisting of polyamide and-polyimide, wherein said film has a thickness of from 2 to 3 mils; and c. a layer. of a thermosetting phenolic resin, the thickness of the resinous coating being only sufficient to cover the second layer; and the overall thickness of the tube being between about 3 and 6 mils,

5. The tube of claim 4 wherein theadjacent courses-of the first and second layer are butt joined, the joints of thesecond consisting of hard aluminum and polyimide; and b. a second layer formed from a film of a material selected from the class consisting of polyamide and polyimide.