US1629517A - Method of making tire casings - Google Patents

Description

Patented Ma '24, 1927.

memes c. mnsnann, or it OUN'I. SAVAGE, MARYLAND.

nn'rnon or name 'rnm enemas.

no Drawing.

My invention relates to theproduction of a tire casing suitable for use as anordmary Y pneumatic,

' probably,

or equally effective as a retreading shoe,or as an outer envelope for any fwell-known resilient filler used as asubstitute for air.

Briefly, the basic conception implies the construction of a casing composed of superposed sheetsof rubber, or rubber compounds, or the like, treated in a-novel manher and thereafter incorporated into the casing in an entirely new manner for the purpose of forming a new article of manufacture, less expensive to make than the conventional casing, and in manyways'supe'rior thereto; all as hereinafter fully, explained. I-Ieretofore, casings of the class under discussion have been universally constructed of alternate layers of strength members composed of fabric, either conventional I cross woven, or of the so-called cord stock generally recognized'as superior fol-this purpose, and unifying layers offaivulcanizable rubber medium. This unifying rubber ma of course, be present in the form of a fr ction coating direct upon the fabric. Referring "to the well-recognized me-' chanics of tire design, these strength elements of the fabric (the term' fabric, being employed in its basic sense to denote any form of textile strengthinsertion) are laid up in diagonal relation with respect to the normal surface of the casing wlt-h the d1- rection of the strands of alternating plies running in opposed direction, this arrangement insuring the maximum efficiency; 1

Among the chief defects and objections to the use of fabric insertions in casings may be mentioned: t

'(a) The tendency of the structure to heat under the influence of internal friction,.

chiefly due to the relative movement of 'cord-on-cord and the radically different physical reactions of the fabric and rubber under high stresses. i

(b) The relative inelasticity of the fabric content as compared to rubber, as demonstrated bi -the characteristic rupture of fabric insertions under sudden and severe shocksthis form of accidental destruction being the most common means of ending the life of a tire. Y

(0) The tendency of the fabric to separate in those zones of the casing subjected to the greatest amplitude of flexation, due to the lack of elasticity of the fabric and its Application filed August 29.1;22, Serial massacre.

inability to form aperfect union with the unifying rubber. (d) The tendency of theq'fabric to deteriorate and weaken in the presence. ofconstant fatigue stress, and especially to rot away in the presence of moisture which gains access tot-he fabric plies through surface cutsf i (.e) The difficulty experienced in repairin a break in the fabric, for the reason that sp icing is" impossible, and the expedient of vulcanizing in a new section is of doubtful efliciency and unsightly; and

' (f) Lastly,the expense of using a considerable; amount of fabric content inthe'casing in substitution of rubber. Thecost of high grade frictioned' cord fabric. being, at

this date, approximately three times that of the best grade of rubber, based on gross weight. v

Of course, it is not a new thought to. construct. inner tubes and a certain class of sin .gle tube tires, designed for light duty, wholly of rubber. This has. been practiced both in the form of tubing the stock through an annular die and by sheeting the stock and wrapping it around a mandrel. In either event, resulting in a homogeneous casing useful for certain purposes where the stresses are notgreat or where such stresses are secondarily restrained, as in the case of an inner tube confined by an outer, casing against distorting stresses. But my invention differs from this practice, radically, as presently explained.

Being well cognizant of the above limitations of fabric and of a wholly rubber structure as acasing, it is the object of the present invention to overcome allof the difficulties enumerated, and which have been stated at considerable length in order that the scope of my improvements maybe readily dis: tinguished fromthe prior art. TlIGNQI'lOUS objects of the disclosure will appear in the following description and appended claims without resorting to a detailed summation of them. i

In the description and claims, the term, wholly of rubber, is used in the generic sense to differentiate my structure from the conventional fabric'ins'ert tire, and is sufiicientlyembrasive to include-all compounds of rubber with or without a secondary- .toughening filler, such as finely'divided textile material, fibre, or the like, as a binder.

No drawings are appended for the reason fabric in that a direction of strength that those skilled in the art .will readily understand the several operations and well known mechanical appliances referred to throughout the discussion.

In my invention, intalring the revolutionary step of eliminating the fabric content,

certain fundamental principles of construction best exemplified in the modern cord tire casing,'are taken advantage of, That is, the

. plies helically or diagonally of the core and reversing the direction of the strength grain of superposed plies, all as well understood in the art I Tn'the preparation of stock for my casing the ingredients are compounded, in the presence ,of suitable known chemical elements to build up desired physical characteristics, on the usual hot mill until thoroughly mixed and the batch then treated on smoothhot calender sheeted into thin layers,.preferably to the approximate gauge of frictioned cord fabric. Thissheeted stock is then preferably subjected 'to ascmi-cure which reduces it to i the approximate pliability of frictioned cord first hot lowing this second surface I which now resembles cord fabric, is run.

fabric and at the same time renders it less tackythus more easily handled. After the semi-cure, the sheets are again run through a second set of rollers especially surfaced to finish the sheet under pressure whereby the stock emerges with its surface striated, fluted or grooved in the direction of its length, being thedirection of original length as formed by its passage through the roll calender. Immediately folrolling, the stock,

through a calender for the purpose of receiving its surface coating of vulcanizable rubber, just as fabric stock is prepared for tire building. This surface oating process is only the usual and well recognized frictioning or skim coating operation whereby the nifying binder between ply and ply is affixed. i

After the foregoing calender operations, the fully treated stock is cut on the bias, like any other straight grained stock, and in due course incorporated into the carcass with the same case that attends the use of textile stock. The same apparatus for building and stitching is used, with the only apparent difference that the wholly rubber stock handles and stitches down with greater facility, due to its inherent property of increased pliability. In the building operation, the rubrolls whereby it is like. surface in the direction of the rolled purpose of affording her stock. 'ofiers an added economy over fabno stock inthat the inevitable trim-0d is not wasted, butcan be again milled and reclaimed, Whereas the trim-off of, fabric is practically a dead loss of considerable moment, due to its/high relative price as compared with rubber. l 1

"Upon the completion of the building operation, the formed structure is cured in a conventional mold, either on an air bag, or in place on the building form upon which it was constructed. In the is, of'course, feasible to apply additional members to the 'casing; such as special chafing strips around the bead and lower side walls, a special'stock tread of extremely tough material, or the likeall within the scope of my invention, which is limited to the main structure of the casing. It has been proved, and the possibilities of further development are practically untouched, that the physical properties of rubbuilding process, it

her can be greatly changed bychemical f treatment. In fact, the tensile strength can be increased to such an extent that'the product is admirably adapted to take the place of textile fabric ina casing, in the manner described; this'increasing, by suitable well known chemical processes, of the toughness and tensile strength of the rubber being, of

course, contemplated as a necessary incidental step in my process. In addition to meeting the mere strength requirement, this rubber stock possesses many advantages over fabric when so employed. For instance, a wholly rubber carcass is less liable to heat in service; will not stone bruise and blow out by internal rupture within reasonable limits; the component plies form a perfect union with each other and will not separate, and will not rot out if-moisture is introduced through-a surface out; there being great resistance to fatigue, the casing will not break down due to under inflation, like a fabric tire; a rupture or out can be repaired with facility; and the entire manufacture, both as affecting the cost of labor and materials, is vastly less expensive "than for the conventional tire.

With regard tothe treatment of the sheeted stock for the purpose ofserrating its surface in the direction of its strength grain, it is obvious that the configurations may take a great variety of form. The material could be intermittently slitted; strandedby completed severance;

The chi-get object being to rouglien the strength grain for the a suitable base for the subsequently applied vulcanizable friction treatment to adhere to in an effective manner. It is-recognized that sheeted plastic material develo s a well de-' fined superior strength grain in. the direotion of its rolled or extruded length. This -or merely fluted, or the I binder and cutting the appended principle is taken advantage of by my present conception, as explained, and the second operation of rolling surface impressions in the direction of tends to augment any strength advantage residing therein. In the'application vof the bias cut stock to the casing, in the building process. this direction of grain strength is utilized just as cord fabric is laid up.

In the treatment of the rubber stock, many variations will become apparent to an experienced rubber worker. For instance, the work could be done all on one calender to the elimination of the preferred double process by originally sheeting out the stock on hot rolls, suitably designed to impress the surface of the stock with the linear features characteristic of my invention. Again, the surfacing could be done by a platen press immediately following the primary calendering, and the press be heated whereby semi-vulcanization would result. Also, the stock might, in the first instance, be forced through a parallel slot in an extruding machine die whereby it is delivered in threadlike form to be loosely unified by passing direct through suitable rolls, or the like.

Having thus described my invention, and especially reserving all obvious variations that could be availed of within the scope of claims to accomplish the object sought to be protected, what I claim is:

1. The method of constructing a tire cas ing comprising the following steps: (a) sheeting a chemically toughened vulcanizable compound, (1)) primarily heat treating the sheeted stock, (0) striating the surface of the primary heat treated stock in the direction of the sheeted grain, (d) bias cutting, and surfacing the stock with a vulcanizable unifying binder, (e), assembling the stock with the striae in obliquely disposed arrangement into casing form in superposed plies, curing the assembled structure.

2. The method of constructing a tire casing, comprising the following steps: (a) sheeting a chemically toughened vulcanizable compound whereby the surface is striated in the direction of the length of fiow, biasl tire forming plies, ((1) assembling the plies in simulation of cord tire stock methods obliquely of the circumference of the strucvulcanizlng the assembled casing.

ture, (0

3. The method of constructing a tire casing of tough vulcanizable material simulating the property comprising'the following steps: (a) preparing a chemically toughened" vulcanizable compound whereby stock is produced in sheets having surface striac, 7)) surface coating the stock with a unifying vulcanizable the stock into convenient ply lengths for assembly, (a) assembling the plies in superposed relation with the striae the primary rolled grain in cutting the striated sheet into of textile 'tire insertions,

obliquely laid on the circumference of the casing with alternating ply striae oppositely directed, (d) vulcanizing the assembled cas- 4. Themethod of preparing a tire casing composed of strength members wholly of rubber, comprising the following steps: (a) preparing building plies of a chemically toughened rubbercompound in simulation of cord fabric with a definite grain in one direction, (1)) assembling the plies in union with a unifying medium in superposed relation, (0) vulcanizing the assembled structures. v

5. The method of preparing a tire casing composed of plies of semi-cured stock Wholly of rubber, comprising the following steps: (a) sheeting a vulcanizable rubber compound chemically treated to impart physical properties desirable for tire carcass plies whereby cord-like lines are formed in the direction in which the stock is Worked, (-1)) cutting, surfacing and incorporating said plies into a carcass structure in simulation of any well known method of easing building, (0) vulcanizing the assembled structure. i Y '6. The method of building a tire casing of the class described, comprising: (a) preparing and sheeting an all-rubber compound of high-tensile properties whereby a definite strength grain is established and maintained in one direction, (1)) semi-curing the sheeted material whereby it is rendered less tacky, and deeply striating the surfaces thereof in the direction of the grain, (c) bias cutting the stock with respect to the direction of the grain, (d) surface coating the bias cut stock with a highly elastic vulcanizable binder adapted to serve as a flexible unifying cushion binder between ply and ply, (e) assemblingthe bias cut, coated, stock in casing form-with the direction of grain. obliquely disposed thereof, (7) unifying the assembled structure by vulcanization.

7. The method of building a tire casing of the class described, comprising: (a) preparing and sheeting a chemically toughened allwhereby a preponderant strength grain is established and maintained in one direction, (7)), rendering by a'subsequent operation and striating each surface thereof parallel with the strengtn grain, (0) surface coating the stock with a highly elastic, adhesive. vulcanizable binder adapted to, flexibly unify and cushion ply and ply, assembling the sheeted and coated stock in casing recti-on of grain of each ply sheet is disposed obliquely thereof and at an angle to adjacent. assembled plies. (a) unifying the assembled structure by vulcanization.

In testimony THOMAS C. MARSHALL.

the prepared sheets less tacky,

form whereby the diwhereof I afiix my signature,