US2247794A - Apparatus for treating sheet material - Google Patents

Description

y 1941- A. WALLACH 2,247,794

APPARATUS FOR TREATING SHEET MATERIAL Original Filed May 21, 1936 ANDRE WALL/10H ATTORNEY Patented July 1, 1941 APPARATUS F MA R TREATING SHEET T ERIAL Andre Wallach, Atlanta, Ga., asslgnor to Sylvania Industrial Corporation, Fredericksbllrg, Va a corporation of Virginia Original application m 21, 1936. Serial No.

Divided and this application October 29, 1938, Serial No. 237,653

6 Claims.

The present invention relates to an apparatus for modifying the surface characteristics of sheets of non-fibrous, relatively plastic materials and the article produced thereby.

This application is a division of application Serial Number 81,054, filed May 21, 1936,- entitled Process and apparatus for treating sheet material, which has matured into Patent No. 2,163,642, June 27, 1939.

Wrapping materials formed from non-fibrous, hydrophilic colloidal materials such as cellulose hydrate, cellulose ethers and esters, gelatin, casein and the like are characterized by a high surface gloss, a high degree of transparency, a smooth surface and a relative expansibility. Sheets of such materials tend to stick together when tightly rolled or stacked, especially when stored under pressure or in amosphere which varies with respect to temperature and humidity. The tackiness of such plasticized sheet materials is dependent, among other factors, upon (1) the thickness of the sheets, (2) the nature and amount of the plasticizer and (3) the temperature and relative humidity of the ambient atmosphere. Under the same atmospheric conditions, a thick sheet can tolerate a larger percentage of plasticizer than a thin sheet. Thus with sheets of cellulose hydrate varying in thickness of from approximately 0.0008 to 0.0016 of an inch, the glycerine content varies correspondingly from about 11% to 19%.

The amount of plasticizer is varied with the seasons of the year. Cellulose hydrate sheets plasticized with 12% glycerine will exhibit no objectionabletackiness on a moderate day in spring, while these sheets will stick together on a humid day in summer and will be brittle on a cold and dry day in winter or fall. As the temperature and relative humidity increase, the tackiness of the sheets also increases.

The above-mentioned factors taken together with the smoothness of the sheet materials give rise to numerous difficulties in the use of the materials. For example, when such material is cut into sheets and the sheets stacked, it frequently happens that the contiguous surfaces stick together to such an extent that it is difficult to separate the individual sheets from the stack. Occasionally after prolonged storage, particularly when under pressure, the sheets stick together to such an extent that the stack may become substantially a unitary block of the material so that this action is commonly referred to in the trade as blocking. The sticking together of the sheets greatly decreases the speed of manipulating such materials in manual wrapping and renders it substantially impossible to use such sheets in automatic machines resulting in inconvenience, waste and expense.

It is a general object of the invention to prevent and/or decrease the blocking" of stacked sheets of plasticized non-fibrous materials which have blocked together, whereby to facilitate the ready separation of individual sheets from the stack.

It is a further object of the invention to provide an improved apparatus for treating stacked sheets of non-fibrous, flexible materials to render the sheets insensitive, with regard to blocking" tendencies, to material variations in the amount of plasticizer, the relative humidity and temperature of the ambient atmosphere and to conditions of storage.

It is a specific object of the invention to provide an apparatus for treating stacked sheets of non-fibrous, flexible materials whereby to decrease the tendency of contiguous surfaces of the sheets to stick together and to decrease the tackiness of the surfaces thereof to facilitate the use of the sheets in manual operations and in automatic machinery.

It is another object of the invention to provide an apparatus for reconditioning stacked sheets of non-fibrous materials simultaneously to improve their flexibility and to decrease the tendency of the sheets to stick together.

Other objects of the invention will in part be obvious and will in part appear hereinafter.

It has now been found that stacked sheets of flexible non-fibrous materials may be rendered insensitive to variations in plasticizer, humidity, temperature and storage conditions generally by inserting between contiguous surfaces of the stacked sheets a small amount of a comminuted material. The edges of the sheets in a face of a stack, either before or after they have become stuck together, are subjected to'a blast of a gas containing a comminuted material. If the sheets are too brittle, the stack may be subjected simultaneously or separately to a gas consisting ofor comprising a softening agent of the sheet material. The apparatus of the invention comprises means to produce a current of a gas, such as air, means to disperse in the gas current a comminuted material and means to position a stack of sheets edgewise in the gas current.

For a fuller understanding of the nature and objects of the invention, reference should be had to the following detailed description taken in connection with the accompanying drawing, in which:

Fig. l is a perspective view of one embodiment of the apparatus of the invention;

Fig. 2 is an enlarged sectional view taken on line 2-2 of Fig. 1;

Fig. 3 is a detailed view in section with parts broken away of a side elevation of a part of the apparatus of Fig. 1;

Fig. 4 is an enlarged sectional view with parts broken away of a modification of a part of the apparatus which is illustrated in Fig. 3; and

Fig. 5 is an embodiment of the stack-holding means of the apparatus of Fig. 1.

The apparatus is applicable for treating sheets of various non-fibrous materials, in particular,

colloidal materials swelling in water such, for

example, as cellulose hydrate, hydroxy-alkyl derivatives of cellulose, gelatin, casein and the like; as well as cellulose derivatives such, for example, as cellulose acetate, cellulose nitrate, methyl cellulose and benzyl cellulose; also rubber and synthetic resins such, for example, as polymerized vinyl resins. glyptal resins and other nonfibrous sheet materials. It is to be understood that such sheet materials may or may not con tain suitable plasticizers, fillers, and may or may not be coated and/or impregnated with waterproofing and moisture-proofing compositions.

For the comminuted material there may be employed an inorganic or organic solid, preferably one which is cheap, non-hygroscopic and relatively soft so as not to scratch the surface of the sheet materials, the parts of automatic machinery in which the treated sheets may be used, or articles wrapped therein. Suitable comminuted materials are inorganic substances such as barium sulphate, zinc oxide, talc, fullers earth or organic substances such as flour, starch, dextrine, anthracene, alkali metal earth soaps, as well as comminuted material of like character to the sheet material such as cellulose hydrate, cellulose derivatives, gelatine, casein and the like. While there is'a wide range permissible in the size of the particles of the comminuted material, it has been foundpreferable, in order to obtain the correlated results herein described without interfering. with the generally accepted uses and properties of the sheet material, to employ material in the form of a powder, the particles of which are not substantially greater than those which will pass through a 100 mesh screen and may have a size corresponding to 200 mesh or more. The comminuted material is applied uniformly over the surfaces of the sheet material in a very small amount, preferably in an amount insuiiicient materially to detract from the normal appearance of the sheet material.

Referring to the drawing, Fig. 1 is a perspective view of one embodiment of an apparatus suitable for carrying out the process, in which a current of a gas may be supplied from a cylinder l having a valve I I, the gas flowing through a flexible conduit I2 having a pressure gauge l3 to a manifold M and to a plurality of outlet nozzles |--|5. The comminuted material It contained in a vessel I1 is sucked into the pipe |2 adjacent the manifold M or directly into the manifold through a pipe la, the bottom end of which dips into the comminuted material. The stack I! of sheets is supported upon a bed plate 20, preferably pivotally supported upon a stand 2|. The bed plate is provided with a fixed back plate 22 and end plates 23 and 24. The end plate 23 is provided with conventional means to adjust its distance from the plate 24. A top plate 25 is preferably supported on the end plate 24 by conventional means (not shown) for adjusting its height from the bed plate 20 whereby to accommodate stacks of different heights therebetween. The end plate 24 is provided with a plurality of slit-like openings 2626 corresponding in spacing and size tothe several nozzles |5--|5. The bed plate 24, being pivotally mounted on the stand 2|, is provided with means such as a rod 21 sliding in a sleeve 28 to vary the inclination thereof. To allow the bed plate to be pivotally moved the pipe |l should be formed of flexible hosing or have a flexible section therein and the pipe l2 should be provided with a suitable union or flexible section.

In the operation of the apparatus, a stack IQ of sheets is placed on the bed plate 2| flush aganst the back plate 22 and end plate 24. The end plate 23 is then moved toward the plate 24 until the edges of the sheets in a face of the stack are firmly pressed thereagainst. If the sheets in the stack are firmly stuck together or blocked, it is preferably first to knead or flex the stack across the straight edge 20 of the bed plate 2|) so as to loosen up the stack.

In operating the apparatus, the valve H is opened and the gas current causes the comminuted material I in the vessel I! to be sucked through the pipe I8 and into the manifold M where it is dispersed in the gas. The gas containing the dispersed comminuted material passes from the nozzles |5|5 through the openings 26-26 against the edge 30 of the stack I9 of sheets, as shown in Fig. 3. The force of the current of gas causes the individual sheets 3| of the stack l9 to separate and the gas passing between the sheets deposits the particles 32 of the comminuted material on the surface of the sheets.

There is shown in Fig. 4 a modification of the apparatus of Fig. 1 in which there are provided means for forcing the stack I9 to assume the shape of a trapezoid so as to produce a progressive overlapping or offset of the successive sheets at the end as shown. The end plates 23 and 24 may be inclined at an angle, preferably less than with respect to the bed plate 20 so that the edge 30 of the stack which is positioned in the current of gas is overhanging as shown in Fig. 4 which facilitates the entrance of the gas between the sheet. As a result of this novel arrangement, the entrance of the gas between the continuous sheets is facilitated.

Another way of facilitating the separation of the sheets is to provide means to flex or corrugate the stack. For example, the bed plate 2| and the top plate 25 may be provided with alternating ribs 33 which function to flex the sheets one or more times, or corrugate the stack as shown in Fig. 5. When the stack is thus flexed or corru gated, air spaces 34-34 are formed between adjacent sheets at intervals in the stack where the sheet changes direction intermediate of opposing ribs as shown in the drawing.

If the stacked sheet material is found to be dried out and brittle, the gas used for separating the sheets may advantageously consist of or comprise a known softening agent of the material and such treatment may be made simultaneously with or subsequent to the treatment with the comminuted material. For example, a suitable water aspirator is attached to the gas line l2 and there is formed in the manifold l4 a mixture of air, water vapor and comminuted material of nonhygroscopic character. This mixture is suitable for separating and simultaneously resoftening brittle sheets of regenerated cellulose. On the other hand, a mixture of air and alcohol vapor may be used with suitable comminuted material for separating and softening sheets of cellulose acetate.

For the compressed gas cylinder I there may be substituted an air compressor with a suitable motor to operate the same in a known manner. The gas pressure required to provide a suitable current will vary with the sheet material and the condition of the stack at the time-of treatment. In the appended claims, the expression gas curren is intended to cover a current of suflicient volume and force to cause a separation of the sheets in the stack being treated.

The stack may be slightly inclined from the horizontal or positioned substantially vertically in the supporting means and the lower edges of the sheets subjected to the blast of gas containing comminuted material by a suitable apparatus embodying the features of the invention. When disposed in this manner, the effect of gravity is partly overcome and the separation of the sheets facilitated. To further facilitate the separation of the sheets, the end plate 24 may be cut out at a point intermediate its ends so that the edges of the sheets in the stack may be riflied by hand while the gas current is played against the edges of the sheets. If desired, the end plate 23 may be suitably perforated to allow ready passage of the gas through the stack or the openings 2626 may be placed in the back plate 22, particularly when the stack is to be positioned substantially vertically.

The product treated with the apparatus of the invention is not materially altered in its general appearance. When a transparent material is treated with particles of a size corresponding to 100 mesh or above, the deposit of comminuted material is practically invisible, the transparency and lustre of the sheet being substantially unimpaired. The sheets in the treated stack are free-flowing and may be separatedeasily by hand or automatic devices.

It appears probable that the various novel characteristics exhibited by the treated material may be ascribed in part to the presence of the particles anchored on the surface, and in part to the pockets of air provided by them, which latter decrease the adherence by preventing the direct contact of large smooth surface areas.

Since certain changes may be made in the above construction and different embodiments of the invention could be made without departing from the scope thereof, it is intended that all matter contained in the above description or shown in the accompanying drawing shall be interpreted as illustrative and not in a limiting sense.

Having described my invention, what I claim as new and desire to secure by Letters Patent is:

1. In an apparatus for treating a stack of sheet materials to render the individual sheets separable, the combination of means to produce a current of a gas, means to disperse a comminuted material in said current and means to position a stack of sheets edgewise in said current so that an edge-face is disposed at an oblique angle to the direction of flow of the gas thereagainst.

2. In an apparatus for treating a stack of sheet materials to render the individual sheets separable, the combination of means to produce a current of a gas, means to disperse a comminuted material in said current, and means to position a stack of sheets edgewise in said current with the sheet edges progressively offset so that the comminuted material will be inserted" between th sheets.

3. In an apparatus for treating a stack of sheet materials to render the individual sheets separable, the combination of means to produce a current of a gas, means to disperse a comminuted material in said current and means to position a stack of sheets edgewise in said current with the sheet edges progressively offset comprising obliquely positioned plates to engage the sheet edges on opposite sides of the stack.

4. In an apparatus for treating a stack of sheet materials to render the individual sheets separable, the combination of means to produce a current of a gas, means to disperse a comminuted material in said current and means to position a stack of sheets edgewise in said current comprising a plate to engage a surface face, edge-face confining plates and a confining plate to engage the other surface face, the surface face engaging plates having alternating ribs thereon for corrugating a stack of sheets confined therebetween.

5. An apparatus for treating a stack of sheets to render the individual sheets separable, comprising means to support the stack of sheets and restrain movement thereof parallel to the plane of the sheets in a given direction, means positioned to direct a current of gas substantially in said given direction against the edges of the sheets in the stack, means for supplying a current of gas to said directing means, and means to disperse a comminuted material in said gas current whereby the comminuted material will be inserted between the sheets.

6. An apparatus for treating a stack of sheets to render the individual sheets separable, comprising means to support the stack of sheets and restrain movement thereof parallel to the plane of the sheets in a given direction, means positioned to direct a current of gas substantially in said given direction against the edges of the sheets in the stack, means for supplying a current of gas to said directing means, means to disperse a sheet softening agent in said gas current and means to disperse a comminuted material in said gas current whereby the comminuted material will be inserted between the sheets.

ANDRE WALLACH.

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