US 2661543 A
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1366- 1953 J. M. TYNDALL EI'AL APPARATUS FOR AND METHODS OF DRYING LEATHER Filed June 24, 1950 In men Ions Joseph M Tyndall Mz'ezh Maeser' By Th z'r-Azz rney Patented Dec. 8, 1953 UNITED STATES PATENT OFFICE APPARATUS FOR AND METHODS OF DRYING LEATHER Application June 24, 1950, Serial No. 170,206
This invention relates to apparatus for and a method of reducing the water content of hides and skins, and more particularly to an improved apparatus for and a method of drying leather in spread-out condition.
Tanned hides or skins, during their manufacture, must be dried at least once and perhaps several times. Heretofore, it has been the practice to stretch, spread or slick out the hides or skins individually on frames or plates preparatory to drying. Each work piece tends to shrink appreciably during drying and in order to avoid such shrinkage or loss in area of the leather, each piece is customarily either toggled to a frame or pasted to a plate as a step preparatory to drying, the toggles or paste maintaining the work piece in extended condition despite the considerable stresses set up as a result of the drying of the leather.
When glass or metal plates are used with paste as the attaching medium, excellent results are secured in that the grain surface is made smooth and highly satisfactory in so far as quality is concerned.
Unfortunately, however, the paste method, while preferred to the use of toggles, is not used for some leathers for various reasons and generally because the paste adheres to the leather after drying and must be removed by washing or buffing. Washing wets the leather again, at least to some extent, and buffing tends to damage the grain surface. It would be highly advantageous if in the use of plates, paste could be dispensed with altogether in maintaining the leather in stretched-out condition for the drying operation. One object of the invention, accordingly, is to provide a novel organization of means for effecting that result. For the purpose in View, two work confining members are provided for compressing and enclosing a leather work piece between them, the surface of one of the members being of a porous material that is vapor-transmissive when wet and the surface of the other member being impermeable to water vapor and having a smooth contacting surface for contacting the grain side of the leather. Associated with the two above-mentioned members is a heating device for driving moisture from the leather, and, in accordance with still another feature of the invention, means is provided for evacuating vapor from the leather being dried and through the porous material contacting the work.
It will be recognized that in a different aspect the invention provides a novel method of drying leather in which heat is applied to the leather While it is maintained in a stretched-out condition and is confined between flat surfaces which are free of paste and with ample provision for the emission of water vapor from the leather.
The invention will now be more particularly described by reference to the accompanying drawing and thereafter pointed out in the claims.
The drawing illustrates one embodiment of a suitable apparatus which may be used in carrying out the present invention. It shows a main supporting plate I0 upon which two rectangular retaining frames i2 and M are attached by suitable fastenings such as the screws I6. Each side member of the frames [2 and I4 is made with a box-like or U-shaped cross section and these frames serve to retain a rigid porous board 20 in spaced relation to the supporting plate HI. An impermeable membrane or rubber sheet 22 is provided as a flexible covering for the porous plate 20. The sheet :22 is laid loosely over the plate 20 with a work piece 23 interposed as further described below. The edges of the sheet 22 are placed in overlapping relation with the top portion of the frame M.
The porous plate 20 may be made of sintered ceramic material or of sintered metal the porosity of which is adequate for the purpose as will be further described. The plate 29 also may be of a laminated construction such as wire mesh or a perforated member (to lend rigidity) with felt for contacting leather to be treated. Regardless of the form of construction adopted for the plate 20 it is essential that the surface to contact the work be of such material that it is vapor-transmissive when wet.
The space between the main supporting plate l0 and the porous plate 20 is determined in extent by the frame !2 and is divided into compartments by crosspieces 30 which are notched, as at 3 2, to cause the compartments to communicate. The bottom of the enclosure (which enclosure is made up of the supporting plate [9, the frames l2 and I4, and the impermeable sheet 22) is provided with a vent 36 which leads to a vacuum pump (not shown in the drawing).
Means are provided for applying heat to the flexible sheet 22 and such means may take the form of infra-red lights, conventional electrical resistance units, or some other form of heater. Conveniently the heater may be and is shown in the form of a duct 4!! for directing hot air over gird in contact with the top surface of the sheet In carrying out the principles of the invention and operating the apparatus as disclosed, a wet leather work piece 23 is placed between the rubber sheet 22 and the porous board 20, as shown in the drawing. Hot air is directed from the duct 40 over and in contact with the sheet 22 and simultaneous with this heating a vacuum is ap- 5 plied and made eflective on the underside-of the plate 20. .This vacuum -iwill be uniform or sub stantially uniform on the entire area of the porous plate 253 because of the baffle effect of the J r dividing strips or cross pieces 39.
Because of the vacuum, moistureandigasesrwill aEI be evacuated from the leather 23 and through-the porous plate 20 and the leather 2 3Wi11.reach-the proper dry condition in a surprisingly 'short time The vacuum not only expeditestheremission of the water from the leather by lowering thew: vaporization point but it also causes the rubber sheet 22 to hold the leather 23 snuglyandfirmly against the plate and prevent it from shrinks ing and losing its area as it dries. 20
When. thedeathenZS has becomeadriedato their; desired extent it may be removed .withitswareal undim'inished and with its grain surface smooth and. attractive; The nature of the grain surface. on the dryiproduct is somewhat dependent uporr25 whether that surface is placed in contact. with the'sheet 22 or with the surfaceof the'boardidr It is preferred, but notessential, thatrthengrainn. surface of rthe'leathe'rr bep1ac'edagainst .the im,-. permeable. "surface and that the flesh surface .be placedin contactwithithe porous plate 2llufor inLSuchJanl arrangementthe. grain surface is smooth and its appearance-is not afiectedlby the possibl'amigratio'n and localized concentration of V the'oilsand other materials in ltheleather.
Ndpaste having been usedain carrying out then-- present invention, each Work piece after being: dried, mayoeasilyrberremoved from'the-apparatus and; it isremovedin clean-condition thereby re-a taining the ladvantagesiof the: conventional past! ,so ing .method. and eliminating the-disadvantages. thr'e0f. It was thought. thatrconsiderable: difi-H: Y cultyi .would' be encountered becauseaof filogging s; of the" pores inthelporous material, particularly: when the nature of wet :leather is brought into m consideration. surprisinglypsuch. difficu1ty has not -..arisen during the. considerable "work along thislliriawhichhas been undertaken.
Having. described our invention,. .what we claim as new. andudesireto secure =byLetters Batent of "5-5;; thUnited-States is: r
l. lIhelmethodrof drying leather: which comsrr prises confining a spreadout wet piece of leather between two flat surfaces, the grain side of said work piece being placed in contact with one of said surfaces which is impermeable to water vapor and the flesh side being placed in contact with the other of said surfaces which is of a porous rmaterial .thatt is vaporetr-ansmissive.when wet, .applying heatito their-said piece of leather and simultaneously evacuating vapor through said-porous material.
2. A leather drying apparatus, having in combinatio'riy'a rigid member having a substantially planesurface on which a workpiece may be spreadnout ia flexible member which is relatively movabl toientirelycover the spread out workpiece; xonerof lsaidemembers being vapor-trans- References "Cit-ed in thefileof "'thisrpatent UNITEI) STATES 'PATENTS Number Nam Date a 921,067: 1,009,881 1,121,265 1,514,926". 1,773,494 1,868,617 2,095,1181 1: 2,321,756 Kyle June 1943 2397, 827 Williams Apia- 2, 1946 2,404,873 Wink ley July-305 1946 2,436;028' Wiegerink Feb3-17f 1948 2,517 ,273 Baker z; Aug. '1, 1950 FOREIGN PATENTSTii Number 1 Country Date 672,156 Germany; Reba:25;s1939=:f-: