US 1756993 A
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y 6,1930. c. E. RAHR 1,756,993
PROCESS OF MAKING PANCAKEOR BUILT-UP SHEET LEATHER Filed May 29, 1925 Patented May 6, 1930 UNITED STATES CHESTER E. RAHR, 0F BROOKLINE, MASSACHUSETTS, ASSIGNORTO. THE FLINTKOTE COMPANY OF BOSTON, MASSACHUSETTS, A CORPORATION 01 MASSACHUSETTS raocessor MAKING PANCAKE Application filed May 29,
This invention relates to the manufacture of built-up sheet leather, or pancake so called, which may be employed in the manufacture of counters, heels, slip tops, and inner soles. Such sheet leather is generally. made of scraps or trimmings of thin leather, sometimes called levellings, produced in splitting or skiving. leather to reduce it to a uniform thickness. The levellings are usually in sheets, varying in thickness from that of a sheet of paper to of an inch, and may be of any shape. These levellings heretofore have been pasted together by flour and dextrine, or starch paste, in a pan or frame, to form a block or cake. The cake was then subjected to pressure, which forces out the greater part of the water, and was hardened by drying. The hardened cake is known as built-up or pancake leather.
As-is quite obvious from the brief description given, one of the very important factors entering into the production of pancake of good quality is the character of the binder employed for pasting the trimmings or levellings together. For example, in the manufacture of'counters from pancake, the paste should be of a quality to ensure a strong yet flexible counter. During the moulding of the counter, if the usual paste is too dry, and thus brittle, breaks inthe-back and heel flange of the counter may occur; while if the paste is in too wet a condition, a warped and illshaped finished counter will result after the drying operation. Moreover, due to the use of binders which lose their binding properties under the action of water, pancake leather has been used only in shoes of the poorest grades, and its wearing qualities were very poor. In fact, due to the unsatisfactory characteristics of pancake leather and to the high labor costs in itsmanufacture within recent years, as well as because of the introduction of other and more satisfactory substitutes, the manufacture of built-up leather of this character has been decreasing.
The object of this inventionis to produce pancake leather which is strong and yet flexible, which not disintegrated when subjectedto the action of water, and which more closely simulates solid leather than the ordinary pancake as heretofore produced. -ject, briefly. stated, is accomplished by em- I ploying as a binder for the leather levellings: 4
0R BUILT-UP SHEET LEATHER 1925. Serial No. 38,827.
i This oba dispersion of'normally adhesive thermoplastic material, preferably asphalt This dispersion or emulsion may consist of an ad 'hesive binder, such as asphalt, the asphalt being subdivided into minute or colloidal particles, and an emulsifying? agent suchi'as colloidal'clay, the particles of asphalt beingprotected or enveloped by the clay, and a liquid vehicle'or medium, such as water. The
emulsion may bemade by the process described in U. S. Letters Patent No. 1,417,835,. granted May 30, 1922', to Lester Kirsch-- braum. Such a suspension or dispersion is non-adhesive, and may be made in paste or plastic form, so that itis capable of being spread or painted on the surface of material.
With the elimination of'water by heat or by the action of heat and pressure, the asphalt particles coalescerand revert to their normally adhesive and cohesive state, and on being thereaftersubjected to water remain water:
proof and are not disintegrated. Pancake may be built up with such a binder and'yield a good product, superior to the heretofore commercially known pancake. On the accompanying drawings Figure 1 represents more or less conventionally a somewhat enlarged section through a portion of pancake leather just after it has v been made as hereinafter described.
Figure 2 is a similar view but shows the cake after it has been pressed and surfaceskived to a uniform thickness.
Figure 3 shows in perspective and more or less conventionally, for purposes of illustration, a counter made with the finished prod- Before building pp the cake, the leather stock may, if desir be tempered or softened with water. The pancake may then be built in a frame. The workman starts by laying a sheet of thin leather that is cut somewhat longer and wider than the frame, and covers it witha coat ,of bituminous emulsion, as by a paintin dipping or spraying operation. A layer ot 'the smallr pieces of leather levellings is then distributed evenly over thempanca tire area of the frame, and coats of emulsion and layers ofleather are laid alternately until the desired thickness of cake is obtained,-
The pressing may then be accomplished by a mechanical or hydraulic press, by means of which heavy pressure may' be applied A layer of these pancakes is placed on a steel plate and is covered, if desired, with a sheet of burlap. Another steel plate is put on, then another layer of pancakes and burlap, and so on until the press is filled. Pressure is applied, and the greater part of the excess water in the cakesis pressed out and the cakes tight-1i compacted. The now firm but damp pressure in the press,-as by heating the press, or ma be removed and hung up ina steamheate loft to dry. In either case, with the elimination of water the asphalt particles coalesce and become adhesive, binding the leather levellings together.
When dry, the pancake is hard and stiff, but
there is a certain amount of pliability and flexibility which is imparted to it by the coalesced asphalt particles, and'it is not as brittle as the ordinary pancake as heretofore made. When tempered and softened in water before being worked, as for example, in the production of counters, there is no tendency for the cake to disintegrate after it is in preper tempered condition, even after a prolonged soakin in water. The cake may be reduced to a uniform thickness as shown in Fig. 2, by a surface skiving machine, and may be cut into blanks for counters on a dinking machine. One side of each blank is usually formed by the whole iece of leather which forms the bottom of t e pancake, and the other,-which is the pieced side, is made up as the inside of the finished counter. The blanks may be skived onthe pieced side and waxed on the outside, and then moulded into shape and the heel flange turned, thus completing the entire counter-forming operation, Figure 3 illustrating a counter thus formed." The material may be freely tempered, because there is no tendency of the asphalt binder to be disin-' tegrated by the moisture, and since the as- I no phalt possess a. certain amount'of flexibility,
the material is not subject to cracking as with the ordinary binders. v
When the hardened and dry cake is used for the manufacture of heels, it is cut into 'heel blanks by the usual cutting dies and built up. The heel will be waterproof.
e may then be dried under heat and .It may be stated that by the use of the expression bituminous emulsion, as used in Y the appended claims I mean a suspension or dispersion in water of normally adhesive and cohesive bituminous material, preferably asphalti the particles of asphalt being of minute or co by colloidal clay or other equivalent emulsifying or colloidal agent, the suspension or dispersion bein non-adhesive and preferably in a pasty or p astic form, so that it may be spread or painted on a surface. On the elimination of the water and on being subjected to heat and pressure, or both, the asphalt coa lesces and reverts to its normal adhesive and cohesive state.
By the term thermoplastic material, I mean any bituminous or pitchy material, such as natural and blown asphalts, stearin itches, or other equivalent materials, so tenable when heated and possessing waterproofing characteristics; and by the term colloidal or emulsifying agent, I mean hydrophilic colloids, such as colloidal clay, soaps, sodium silicate, glue, gums, starch paste, and the like.
Having thus described an embodiment of this invention, it should be evident to those skilled in the art that it is susceptible of various changes and modifications without departing from its spirit or scope as defined by the appended claims.
What I claim is:
1. A process of making built-up or pan cake leather from thin leather, which comprises applying a coating of a dispersion of a thermoplastic binder in water to the surfaces of the thin leather and building up a plurality of layers of such coated leather tempered and softened by the water component of said dispersion.
2. A process of making built-up or pancake leather from thin leather, which comprises applying a coatin or film of bituminous emulsion in non-a hesive form to the surfaces of the thin leather, building up a plurality of layers of such coated leather, applying pressure to the built-up layers, and applying heat to coalesce the bituminous material and to unite the layers.
3. A process of making built-u or pancake leather from thin scrap leat er, which comprises applying a coating or film of a disloidal size and protected or enveloped.
person of asphalt in water to the surfaces of l the thin leather, building up a plurality oflayers of such coated leather, and then drycake leather from thin scrap leather, which comprises coating the surfaces of such scrap leather with a dispersion of a thermoplastic v binder containing water in the external phase,
building up a plurality of layers of such'co'ated leather tempered and softened by the water content of said dispersion, and then pressing and heating the built-up layers to remove the water and coalesce the previously dispersed particles of binder.
In testimony whereof I have affixed my signature;
CHESTER E. RAHR.